In vitro fertilisation in Switzerland: what happens in the laboratory

Behind every in vitro fertilisation is a laboratory where embryologists handle, under the microscope and in strictly controlled conditions, what is most precious to a couple: their eggs, their sperm and then their embryos. Understanding what happens in the laboratory helps couples cope better with the process, interpret the information they receive after egg collection and ask the right questions. This page describes, step by step, the work of the IVF laboratory: gamete preparation, conventional fertilisation or micro-injection, embryo culture and assessment, vitrification, preimplantation genetic testing, quality and controls, within the framework of Swiss law. For an overview of the whole process, see our IVF and assisted reproduction guide.

In the laboratory, the eggs retrieved during egg collection are identified and then fertilised either by placing them in contact with the prepared sperm, or by micro-injecting a single sperm into each mature egg. The embryos are cultured in incubators that reproduce the conditions of the body and observed every day for five to six days. One embryo is transferred and the other good-quality embryos are vitrified. In Switzerland, the law limits the number of embryos developed per cycle to twelve and regulates their storage. IVF laboratory procedures are paid for by the couple. Budget guidelines are on our page in vitro fertilisation prices in Switzerland.

The term "in vitro" literally means "in glass". It refers to the fact that the meeting between egg and sperm, which naturally occurs in the fallopian tube, takes place in the laboratory, in a culture dish. The first days of the embryo's development also take place outside the body, before it is transferred to the uterus.

In vitro fertilisation relies on close collaboration between the doctor, who stimulates the ovaries, collects the eggs and transfers the embryo, and the laboratory, which handles all the intermediate stages. The quality of this laboratory, its equipment, its procedures and its team is one of the factors that influence the chances of success.

Many couples experience the days between egg collection and transfer as a black box, where important decisions are made far away from them. Understanding what happens in the laboratory (why some eggs are not fertilised, why some embryos stop developing, what the grades mean) makes it easier to interpret the information received, reduces the anxiety of the unknown and allows couples to take an active part in decisions. It is also a way of recognising the work of a team that is often invisible.

For the man, the laboratory is often where he participates most concretely in the process: semen analysis, sperm migration-survival test, sample collection on the day of egg collection, and sometimes prior freezing or surgical sperm retrieval. These moments can be experienced with embarrassment or stress. Laboratory teams are used to supporting men through them discreetly. Understanding how his sperm is prepared and used also helps the man feel fully involved in the project.

For the woman, the IVF journey consists of injections, ultrasound scans, egg collection and transfer. Between egg collection and transfer, her eggs become invisible, entrusted to the laboratory. Knowing that they are cared for attentively, observed every day, and that every decision is carefully considered, can ease some of the worry. Asking for a photo of the transferred embryo also helps some women picture this stage more clearly.

Despite the high technology, the work of the IVF laboratory remains deeply human: it is the eyes, hands and experience of the embryologists that locate the eggs, choose the sperm, assess the embryos and make the decisions. Many of them are aware of what each embryo means to a couple, and they often learn with emotion of the pregnancies that result from their work.

The first birth after in vitro fertilisation, in 1978 in the United Kingdom, was the result of many years of laboratory research into egg maturation and embryo culture. In the 1980s, embryo freezing and improved culture media broadened the possibilities. In 1992, the first birth after ICSI revolutionised the treatment of male infertility. The 2000s saw blastocyst culture and vitrification become widespread, which considerably improved results.

Today, research continues into embryo assessment, incubators, genetic testing and artificial intelligence. The laboratory remains at the heart of progress in IVF.

In Switzerland, the first births after in vitro fertilisation took place in the 1980s in university centres. The practice was then regulated by a constitutional article, and then by the Federal Act on Medically Assisted Reproduction, which came into force in 2001. For a long time this law imposed strict rules on the laboratory, notably on the number of embryos developed. Its revision, approved in a popular vote in 2016 and in force since 2017, authorised preimplantation genetic testing and raised the maximum number of embryos developed per cycle to twelve, facilitating single embryo transfer and freezing.

Before 2017, Swiss law severely limited the number of embryos that could be developed per cycle, which often meant transferring several embryos or freezing eggs at an early stage. Relaxing this rule enabled Swiss laboratories to practise blastocyst culture and vitrification as elsewhere, with single embryo transfer becoming more systematic. These changes show the direct influence of the legal framework on laboratory work.

Before 2017, because Swiss law limited the number of embryos that could be developed, laboratories often froze so-called impregnated eggs, i.e. fertilised but before the fusion of the nuclei, a stage not yet considered an embryo within the meaning of the law. Some couples still have impregnated eggs stored from that period. They can be thawed and cultured to obtain embryos, in accordance with the rules in force. The centre will inform you of the options available to you.

Today, Swiss laboratories routinely practise blastocyst culture, vitrification of embryos and eggs, ICSI where indicated and, in licensed centres, preimplantation genetic testing. Single embryo transfer is the rule in most situations. These practices, comparable to those of other European countries, operate within one of the most tightly regulated legal frameworks, which protects both couples and embryos.

The IVF laboratory continues to evolve: automation of certain tasks, imaging and artificial intelligence to assess embryos, less invasive genetic testing, improved culture media and new approaches to fertility preservation. These advances will need to be rigorously evaluated before becoming routine practice. What will not change is the importance of human expertise, rigour and the attention paid to each couple.

In intrauterine insemination, the laboratory simply prepares the sperm, which is then placed in the uterus: fertilisation takes place naturally in the fallopian tube, and the laboratory does not handle the eggs or embryos. In IVF, by contrast, fertilisation and the first days of development take place in the laboratory. See our page on artificial insemination.

Some approaches reduce stimulation: in a natural cycle, the single egg produced spontaneously is collected; in mild stimulation, the aim is a few eggs with lower doses. For the laboratory, these cycles mean fewer eggs and embryos, and therefore less choice and fewer embryos to freeze. They may suit some women, for example those with a low ovarian reserve or a contraindication to high doses, with lower chances per cycle but lighter treatment.

An in vitro fertilisation laboratory is designed to protect gametes and embryos from anything that might disturb them. The air is filtered to remove particles and volatile compounds, the temperature of work surfaces is kept close to body temperature, lighting is dimmed, and handling takes place under controlled-airflow hoods. Materials in contact with the embryos are tested for safety.

The incubators constantly maintain a suitable temperature, humidity and gas composition, notably a reduced oxygen concentration closer to that of the fallopian tubes and uterus. These parameters are recorded and monitored by alarms, day and night.

Every day, the embryologists check the temperature of the incubators and surfaces, the gas concentration and the nitrogen level in the tanks, and record these values. The equipment undergoes regular preventive maintenance and calibration. New batches of media and materials are checked before use. These routines guarantee a stable environment and allow an immediate response in the event of any deviation.

A typical day in the laboratory starts early: equipment checks, observation of the day's embryos, preparation of transfers. Egg collections follow one another in the morning, followed by sperm preparation and insemination in the afternoon. In between, the embryologists perform ICSI, vitrifications, warmings and biopsies, and keep couples informed. The pace is dictated by embryo biology, which knows neither weekends nor public holidays.

Embryos develop in culture media, liquids that provide them with salts, sugars, amino acids and other necessary elements, at a controlled acidity. Some laboratories use a single medium for the entire culture, while others change medium on day three to adapt to the embryo's needs, which evolve as it develops. The drops of medium are covered with oil to limit evaporation and fluctuations.

These media are regulated medical devices, manufactured to strict standards and checked batch by batch. The laboratory chooses those that have demonstrated their effectiveness and monitors their performance.

Before any treatment, blood tests are carried out on both partners for certain transmissible infections, such as HIV and hepatitis. These results allow the laboratory to apply appropriate measures: handling under specific conditions and, if necessary, storage of samples in dedicated tanks, to prevent any cross-contamination. Thanks to these procedures, couples affected by a chronic viral infection can undergo IVF safely.

The air we breathe contains about twenty-one per cent oxygen, but the concentration in the fallopian tubes and uterus is much lower. Many laboratories therefore culture embryos in a low-oxygen atmosphere, around five per cent, which is closer to natural conditions and appears to promote their development. This is one example of the many invisible settings that influence the quality of the culture.

Embryos are highly sensitive to variations in the acidity of the medium, which is controlled by the carbon dioxide concentration in the incubator, and to variations in temperature. Laboratories check these parameters daily, warm work surfaces and instruments, and limit the time spent outside the incubator. These precautions, barely visible to couples, are among the factors that distinguish a high-performing laboratory.

The drops of medium in which the eggs and embryos are bathed are covered with a thin layer of specially purified oil. It limits evaporation, stabilises temperature and acidity, and protects the embryos from environmental fluctuations during observations. Like the media, this oil is checked for safety.

Patient safety relies on rigorous traceability. Every tube, dish and straw bears the couple's identity; every transfer from one container to another is checked by a second embryologist or by an electronic identification system. Dates, times, operators and observations are recorded. Before the transfer, identity is checked with the couple. These procedures make identification errors exceptional.

The sperm cell is a very particular cell, made up of a head containing the father's genetic material and a pouch of enzymes, a midpiece rich in mitochondria that provide energy, and a tail (flagellum) that gives it mobility. Its production, spermatogenesis, takes about seventy-four days in the testicle, after which the sperm mature in the epididymis.

To be able to fertilise, the sperm must undergo a transformation called capacitation, which occurs naturally in the female reproductive tract and which laboratory preparation partly reproduces. Only a small fraction of the sperm in an ejaculate is actually capable of fertilising.

In the laboratory, the semen is first left to liquefy and then analysed: volume, concentration, motility. It is then prepared, most often by density gradient centrifugation, which separates motile, morphologically normal sperm from the seminal fluid, cells and immotile sperm, or by the swim-up technique, in which the most motile sperm swim into a clean medium.

The resulting concentrated and purified preparation is adapted to the chosen technique: a few tens of thousands of motile sperm per egg for conventional IVF, or a small amount sufficient to select one sperm per egg for ICSI.

In many centres, an andrology laboratory, sometimes separate from the IVF laboratory, performs semen analyses, migration-survival tests, additional sperm tests and sperm freezing. Its results guide the choice of technique. It works closely with the IVF laboratory and the urologist or andrologist following the male partner. For the man, it is often the first contact with the assisted reproduction process.

• Observe the abstinence period indicated, usually two to five days.
• Avoid alcohol and tobacco in the preceding days.
• Report any recent fever or medication.
• Wash your hands and follow the hygiene instructions.
• Collect the entire ejaculate in the container provided.
• If collecting at home, respect the time limit and transport temperature.
• Tell the team about any difficulty: solutions exist.

Stress about producing a sample on the day of egg collection is common; freezing a sample beforehand can be reassuring.

On the day of egg collection, the pressure can make producing a sample difficult for some men. This is common and you should not hesitate to talk about it in advance. Several solutions exist: collection at home if the time allows, freezing a back-up sample before the cycle, medication in some cases or, as a last resort, surgical sperm retrieval. The team is used to these situations and handles them without judgement.

Interpretation is based on all the parameters and on the results after preparation, which show how many motile sperm are actually usable.

These reference values, taken from international recommendations, are statistical benchmarks, not absolute fertility thresholds. A result below them does not mean pregnancy is impossible, and a normal result does not guarantee it. The embryologist interprets the overall picture.

The migration-survival test assesses how many motile sperm can be obtained after preparation, and how many survive after twenty-four hours. It helps choose the most suitable technique: insemination, conventional IVF or ICSI. It is a practical test that reproduces the preparation carried out on the day of treatment.

Sperm quality varies naturally from one sample to another, depending on the length of abstinence, a recent fever, stress, medication or exposure to heat. A fever can affect production for several weeks, as spermatogenesis takes about two and a half months. This is why an abnormal semen analysis is often repeated, and why lifestyle changes take a few months to be reflected in the results.

Several techniques aim to select the best-quality sperm for ICSI: very high magnification observation of head shape, selection based on the ability to bind to a substance found around the egg, sorting using magnetic columns or microfluidic devices that mimic the natural path of sperm. They may be of value in certain situations, such as repeated failures or severe abnormalities.

For most couples, their benefit on birth rates has not been clearly demonstrated, and they increase the cost. Ask the embryologist whether they are relevant in your case.

The egg is the largest cell in the human body, barely visible to the naked eye. It is surrounded by a protective shell, the zona pellucida, and by nourishing cells that form the cumulus. In addition to the mother's genetic material, it contains most of the reserves and machinery needed for the first days of the embryo's development, which explains its decisive role in embryo quality.

At ovulation, or at the trigger in IVF, the egg completes a stage of its maturation and expels a small body, a sign that it is mature and ready to be fertilised.

A few benchmarks are enough to grasp the precision of laboratory work: an egg measures about a tenth of a millimetre, a sperm cell about five hundredths of a millimetre long, but its head only a few thousandths. The pipette used for ICSI has a diameter of a few thousandths of a millimetre, much finer than a hair. A blastocyst measures about two tenths of a millimetre. These scales explain the need for powerful microscopes, precision instruments and extensive experience.

Each egg must pass on exactly twenty-three chromosomes. During its maturation, the chromosomes are divided between the egg and a small expelled body. With age, the mechanisms that ensure this division become less reliable, and the proportion of eggs with an abnormal number of chromosomes increases markedly after 35, and even more after 40. The resulting embryos often stop developing, fail to implant or lead to miscarriage.

This is the main biological explanation for the decline in chances with age, and the reason why the laboratory cannot fully compensate for the effect of age, even with the best techniques.

In a young woman, the laboratory often has several good-quality embryos, and its role is to select the best one and store the others. In a woman over 40, it often has fewer eggs, a large proportion of which carry chromosomal abnormalities; it cannot correct them. It provides the best culture conditions, but the chances remain limited by the biology of the eggs. This reality, sometimes hard to hear, must be explained honestly.

The laboratory cannot improve the quality of eggs and sperm, but the couple can act beforehand, in the months leading up to IVF: stop smoking, limit alcohol, aim for a healthy weight, avoid drugs and anabolic steroids, take folic acid (for the woman), limit exposure to heat (for the man) and treat chronic diseases. These simple but effective measures give the gametes the best chances even before they arrive in the laboratory.

Mitochondria, small power plants present in large numbers in the egg, provide the energy needed for maturation, fertilisation and the embryo's first divisions. Their function declines with age, which may contribute to the decline in egg quality. Approaches aimed at improving this energy have been studied, but none has shown sufficient effectiveness to be recommended in routine practice.

During egg collection, the fluid aspirated from each follicle is passed immediately to the laboratory, often through a hatch connecting the collection room to the laboratory. The embryologist examines this fluid under the microscope and locates the complexes formed by the egg and its nourishing cells. Each egg found is washed and then placed in culture medium in the incubator. The doctor is informed in real time of the number of eggs retrieved.

A few hours later, depending on the planned technique, the eggs are either inseminated with their cells, or stripped of them to assess their maturity and perform ICSI.

Ovarian stimulation, managed by the doctor, makes several follicles grow at the same time, each containing an egg. The timing of the trigger is chosen so that as many eggs as possible are mature at the time of egg collection, about thirty-six hours later. The laboratory then observes the outcome of this stimulation: number of eggs, proportion of mature eggs, appearance. This information is valuable to the doctor, who can adjust the doses or the trigger in a subsequent cycle.

Doctor and embryologist thus form a team: one prepares the eggs, the other receives them and makes the most of them, and each keeps the other informed.

Each follicle contains fluid that bathes the egg and the cells around it. During egg collection, this fluid is aspirated together with the egg. It contains hormones and many substances produced by the follicle. Research is trying to find markers of egg quality in it, but no test is yet used routinely to predict an egg's potential.

Before ICSI, the cells surrounding the egg must be removed so that the embryologist can see the egg, assess its maturity and perform the injection. This step, called denudation, combines an enzyme that dissolves the bonds between the cells with fine pipettes that gently detach them. It is carried out a few hours after egg collection. This is when the embryologist finds out how many eggs are mature.

Under the microscope, the embryologist may observe certain features of the eggs: irregular shape, granulation, vacuoles, the appearance of the zona pellucida or of the small expelled body. Some are associated with lower potential, others have no clear significance. These observations are recorded, but they do not allow the egg's fate to be predicted with certainty. They help in understanding the results of a cycle, especially when they recur.

The proportion of mature eggs depends on the stimulation, the timing of the trigger and factors specific to each woman.

In vitro maturation involves retrieving eggs that are still immature, with little or no stimulation, and then maturing them in the laboratory for one to two days before fertilising them. It may be offered to some women at high risk of hyperstimulation, or in certain fertility preservation situations where stimulation is not possible. Results are currently lower than those of conventional IVF, and the technique is only available in certain centres.

Immature eggs retrieved during egg collection cannot be fertilised immediately. Some mature within a few hours and can then be used for ICSI; others remain immature. Embryos from eggs that matured in the laboratory have, on average, slightly lower potential. A high proportion of immature eggs may lead to adjusting the timing or type of trigger in a subsequent cycle.

A cycle sometimes produces many eggs but few good-quality embryos. This may be due to a high proportion of immature eggs, lower egg quality, for example in some cases of polycystic ovary syndrome or with age, or to fertilisation difficulties. Analysing the cycle makes it possible to adapt the stimulation, the trigger or the fertilisation technique in a subsequent attempt.

When few eggs are retrieved, for example in the case of low ovarian reserve, the laboratory pays particular attention to each one. ICSI may be chosen to maximise the chances of fertilisation. Culture to the blastocyst stage or an earlier transfer is discussed depending on the number of embryos. Some teams suggest accumulating embryos or eggs from several cycles by vitrification before transfer. The laboratory cannot increase the number of eggs, but it can optimise their use.

Sometimes no embryo is available for transfer: no eggs retrieved, no mature eggs, fertilisation failure, or all embryos stopping their development. This is a particularly difficult ordeal for the couple. A consultation with the doctor and the embryologist makes it possible to analyse the cause and discuss the next steps: changing the stimulation, changing the fertilisation technique, or considering the real chances of a new cycle. Psychological support is often helpful at this point.

When each cycle produces only a few embryos, some teams suggest carrying out several successive stimulations, vitrifying the eggs or embryos obtained each time, before proceeding with transfers. This strategy may be considered, for example, with a view to preimplantation genetic testing or in the case of low ovarian reserve. It requires several egg collections and increases the cost; its value is discussed on a case-by-case basis.

During natural fertilisation or conventional IVF, the sperm passes through the cells surrounding the egg, binds to the zona pellucida, penetrates it using its enzymes and then fuses with the egg. This fusion triggers a reaction that prevents other sperm from entering and activates the egg. A few hours later, two nuclei appear: one carries the mother's chromosomes, the other the father's. They move closer together, and the genetic material is combined during the first division.

In ICSI, the embryologist bypasses the first steps by placing the sperm directly inside the egg, but activation and the formation of the nuclei follow the same course.

In conventional IVF, two sperm occasionally penetrate the same egg, resulting in three nuclei instead of two the following day. The resulting embryo would have an abnormal number of chromosomes and cannot be used. The fertilisation check, carried out precisely at the right time, identifies these situations. They are less common with ICSI, since only one sperm is injected.

When conventional IVF has fertilised no eggs or very few, some laboratories perform a rescue ICSI the following day on the unfertilised eggs. The results of this practice are lower than those of ICSI performed from the outset, as the eggs have aged by a few hours. It is not offered everywhere. Most often, the failure leads to planning ICSI directly in the next cycle.

In certain intermediate situations, for example borderline sperm or unexplained infertility in a first cycle, the laboratory may split the eggs between conventional IVF and ICSI. This strategy limits the risk of total fertilisation failure while assessing the natural fertilisation capacity, which is useful for deciding on the technique in subsequent cycles.

ICSI is performed under a microscope fitted with micromanipulators, mechanical arms that allow extremely precise movements. The egg is held by a holding pipette; the sperm, chosen for its motility and shape, is immobilised by touching its tail and then drawn into a micropipette with a diameter much smaller than that of a hair. The embryologist passes through the zona pellucida and the egg membrane, deposits the sperm and gently withdraws the pipette.

This procedure requires extensive training and experience. It is repeated for each mature egg. Fertilisation is checked the following day.

ICSI does not improve results when the sperm is of good quality; it is reserved for situations where it offers a benefit.

After the sperm enters, the egg must be activated for fertilisation to continue. In rare cases, despite ICSI, the eggs do not activate, leading to repeated fertilisation failures, sometimes linked to a sperm defect. Artificial egg activation, using substances that reproduce the natural signal, may then be offered in some centres. It is reserved for these particular situations, after analysis of previous cycles.

When sperm are not present in the ejaculate, they can sometimes be retrieved directly from the testicle or epididymis. In the laboratory, the retrieved tissue is carefully broken up and examined under the microscope, sometimes for several hours, to find sperm. These are often few in number and poorly motile, but a single one is enough for each egg in ICSI. They can be used the same day or frozen for later cycles. See our page on testicular biopsy.

The choice depends on the number and quality of the embryos, previous cycles and the laboratory's practices.

When very few embryos are available, some laboratories prefer to transfer on day three, to avoid having no embryo available on day five. Others continue the culture, considering that the laboratory environment is as favourable as the uterus and that extended culture provides information on the embryos' potential. Both approaches are defensible; the embryologist and the doctor will explain their choice.

Sometimes a cycle produces only one embryo. It is then generally transferred, often on day three or at the blastocyst stage depending on the centre. A single embryo can perfectly well lead to a pregnancy. This result also provides useful information for adapting the strategy in a subsequent cycle.

The laboratory stages follow a precise schedule, set by biology: fertilisation takes place a few hours after egg collection, the fertilisation check sixteen to twenty hours later, and embryo observations at set times each day. This schedule makes it possible to compare embryos with one another and with reference standards. It also explains why egg collection and transfer times are set precisely and why the laboratory works every day.

When transfer or freezing takes place on day three, the assessment is based on the number of cells, their regularity and the proportion of fragments, small detached pieces of cytoplasm. A good-quality embryo on day three generally has six to eight regular cells with few fragments. These criteria are less predictive than those for blastocysts, as many embryos that look satisfactory on day three subsequently stop developing.

Some embryos reach the blastocyst stage a little later, on day six or, more rarely, day seven. They can be vitrified and transferred, with chances that are on average slightly lower than day-five blastocysts, but real. Their slower development does not mean they are abnormal. The laboratory sometimes extends the culture to give them time to develop, within the limits of good practice.

Fragmentation refers to the presence of small fragments of cytoplasm between the cells of the embryo. Slight fragmentation is common and compatible with good development; significant fragmentation is associated with reduced potential. It may be linked to egg quality, chromosomal abnormalities or culture conditions. The embryologist takes it into account in the assessment, although it is not decisive on its own.

During the first two to three days, the embryo functions mainly thanks to the reserves and instructions inherited from the egg. Around day three, the embryo's own genetic material, from both parents, takes over and begins to direct its development. This is when many embryos carrying abnormalities stop developing.

This handover explains why egg quality, which is linked to age, is so decisive in the first few days, and why culture to the blastocyst stage makes it easier to identify embryos with good potential.

On day four, the embryo's cells draw together and adhere tightly to one another: this is compaction, which produces the morula. Then, on day five, a fluid-filled cavity forms and the cells divide into two groups: an outer layer, which will form the placenta and associated tissues, and an inner cell mass, which will form the embryo proper. The blastocyst grows, its zona pellucida thins, and it prepares to hatch in order to implant.

A blastocyst measures about two tenths of a millimetre. It is surrounded by the zona pellucida, which thins as it grows. Inside, a layer of flattened cells, the trophectoderm, surrounds a fluid-filled cavity, the blastocoel. Against the wall, a small cluster of rounded cells, the inner cell mass, will give rise to the embryo and then the foetus. The trophectoderm will form the placenta and the membranes. At hatching, the blastocyst emerges from its zona pellucida through a small opening, ready to implant.

Thanks to camera incubators, embryologists have observed that some blastocysts spontaneously contract and re-expand during their development. The significance of these contractions is still being studied: some studies associate them with slightly lower potential, others do not. This is an example of how continuous observation brings new knowledge, which still needs to be validated before it can be used to choose embryos.

It is common for some of the embryos to stop developing between day two and day five. This loss, often difficult for couples to cope with, largely reflects natural selection: embryos carrying major chromosomal abnormalities or a developmental defect stop, as they would in natural conception, where these losses go unnoticed. The laboratory cannot prevent this, but it provides the best conditions for viable embryos to continue growing.

It is worth bearing in mind that the laboratory reproduces, under controlled conditions, stages that take place naturally in the body: the meeting of the gametes in the fallopian tube, the embryo's first divisions as it travels down to the uterus, and then implantation. In natural conception, a large proportion of embryos do not implant either, often without the woman knowing. IVF makes visible these stages and losses, which usually remain invisible. This perspective can help put certain disappointments along the way into context and show that the laboratory supports biology rather than replacing it, with all the rigour and care of its teams, in the service of each couple and their wish for a child, from the first day of culture to the very last, together.

A blastocyst graded 4AA, for example, is considered to be of very good morphological quality, but other embryos with lower grades can also lead to a pregnancy. These grades are mainly used to rank the embryos of the same couple.

Embryos that divide too slowly or too quickly have, on average, lower potential than those that follow the expected pace. At each observation, the embryologist therefore records the number of cells according to the time elapsed since fertilisation. Camera incubators allow these moments to be measured precisely. These data refine the assessment, without making it possible to predict an embryo's outcome with certainty.

Some cells of an embryo sometimes contain several nuclei instead of one. This phenomenon, called multinucleation, is associated with a higher risk of chromosomal abnormalities and reduced implantation potential, especially if it is frequent. It is recorded by the embryologist and taken into account when choosing the embryo, without necessarily excluding the embryo concerned.

Morphological assessment, i.e. the appearance of the embryo under the microscope, remains the most widely used method for choosing the embryo to transfer. It is useful but imperfect: it cannot see the chromosomes or the internal workings of the cells. A perfect-looking embryo may carry a chromosomal abnormality, and an average-looking embryo may be perfectly viable.

That is why embryologists speak of potential and probability, not certainty. They can supplement the assessment with developmental kinetics or, in the situations provided for by law, with genetic testing.

Incubators fitted with a camera photograph the embryos at regular intervals without removing them from their environment. Embryologists can thus watch a film of their development: the timing of each division, regularity, abnormal events. These kinetics provide additional information for choosing the embryo and limit handling.

Software programs, some of which use artificial intelligence, generate scores from these images. Studies have not yet convincingly shown that these systems increase birth rates for all patients. They are available in some centres, sometimes as a paid option.

Artificial intelligence tools are being developed to help assess embryos from images, and even to predict their chances of implantation. In future they could make assessment more objective and reproducible. Today, they remain decision-support aids for embryologists, and their benefit on births has yet to be confirmed by robust studies. The embryologist's eye and experience remain central.

Freezing a living cell is delicate: the water it contains can form ice crystals that damage its structures. In the past, slow freezing was used, cooling embryos gradually, with variable results. Vitrification has transformed practice: after a brief passage through solutions that replace some of the water in the cells with cryoprotectants, the embryo or egg is plunged directly into liquid nitrogen. Cooling is so rapid that the water solidifies without forming crystals, like glass.

On thawing, known as warming, the process is rapidly reversed and the cryoprotectants are gradually removed. The vast majority of vitrified embryos survive and resume their development.

Before vitrification became widespread, embryos were frozen using a slow method that gradually lowered the temperature in a programmable machine. Some embryos did not survive thawing. Embryos frozen with this method many years ago may still be in storage; they are thawed using the corresponding protocol. Today, almost all laboratories use vitrification, which is more reliable, for both embryos and eggs.

In certain situations, a couple may wonder whether it is better to freeze eggs or embryos. Freezing embryos makes it possible to know their development and quality, and gives well-established results. Freezing eggs preserves the possibility of using them with another partner later and avoids creating surplus embryos, but the quality of future embryos remains unknown. The choice depends on the couple's situation, beliefs and plans.

Some laboratories deliberately collapse the blastocyst cavity before vitrification to improve survival. Warming follows the reverse path, in a few minutes.

Vitrified or frozen embryos, eggs and sperm are placed in small labelled carriers and then stored in liquid nitrogen tanks at around minus one hundred and ninety-six degrees. At this temperature, all biological activity is suspended, and samples can be stored for many years without loss of quality. The tanks are continuously monitored by sensors and alarms and regularly refilled. A precise inventory makes it possible to locate every sample.

The storage of embryos and gametes is limited in time by law, with the possibility of extensions on written request. The centre informs you of the deadlines; it is important to keep your contact details up to date and to reply to letters, so that your embryos are not destroyed for lack of a response. Storage fees are generally charged every year. If your plans change, you can inform the centre of your decisions at any time.

If you move or change centre, your frozen embryos or gametes can be transported to another licensed centre. Transport takes place in special containers that maintain the temperature of liquid nitrogen, following secure and traceable procedures. The two centres must organise the transfer together, with your written consent. Transport fees apply.

Liquid nitrogen tanks are continuously monitored by level and temperature sensors connected to alarms that alert the team, including at night and at weekends. They are regularly refilled, inspected and maintained. Some laboratories split the same couple's samples between several tanks to limit risks. These measures make storage incidents exceptional.

On the day of a frozen embryo transfer, the embryologist warms the chosen embryo a few hours before the transfer, or the day before depending on the stage. They check its survival and resumption of development, notably the re-expansion of a blastocyst. If the embryo has not survived, which is rare, another embryo may be warmed as agreed with the couple. The embryo is then transferred as in a fresh transfer.

Even with vitrification, an embryo occasionally does not survive warming or does not resume its development. The embryologist will inform you immediately. Depending on what has been agreed, another embryo may be warmed the same day, or the transfer may be postponed. This remains exceptional, but it is useful to discuss it in advance.

When eggs have been vitrified, for example for fertility preservation, they are warmed on the day of use and then fertilised by ICSI, as their outer shell may be altered by freezing. Some eggs do not survive warming or are not fertilised, and not all embryos reach the blastocyst stage. This is why a sufficient number of stored eggs is important, all the more so if freezing was done at a later age.

For fertility preservation, the laboratory vitrifies mature eggs after stimulation and egg collection, freezes sperm collected before treatment or, in some hospital centres, freezes fragments of ovarian or testicular tissue. Each type of sample follows a specific protocol. Vitrified eggs are counted and described, which helps estimate future chances. These samples are stored under the same secure conditions as embryos, within the time limits set by law.

For some young women or girls who must undergo treatment that is highly toxic to the ovaries, and for whom stimulation is not possible, a fragment of ovary can be removed by laparoscopy and frozen. It contains a very large number of immature follicles. Later, after recovery, this tissue can be regrafted to restore ovarian function and sometimes enable a pregnancy. This technique is carried out in specialised centres.

For boys and young men who must undergo cancer treatment, sperm storage is offered as soon as possible, once puberty is sufficiently advanced. Collection takes place at the laboratory, with age-appropriate support. If collection is not possible, other options can be discussed in specialised centres. This preserves a chance of future fatherhood.

When preimplantation genetic testing is performed, the laboratory's work is adapted: fertilisation is carried out by ICSI to prevent a surplus sperm from contaminating the analysis, and the embryos are cultured to the blastocyst stage. The embryologist then uses a laser and a micropipette to remove a few cells from the outer layer, which will form the placenta, while preserving the inner cell mass. The cells removed are sent to a genetics laboratory, and each blastocyst is vitrified while awaiting the results.

Once the results are known, an unaffected embryo is warmed and transferred in a later cycle. This process requires precise organisation and an experienced laboratory.

The biopsy is most often performed on day five or six, when the blastocyst is well developed. The embryologist positions the embryo so that the inner cell mass is out of the way, opens the zona pellucida with the laser if it is not already open, gently aspirates a few trophectoderm cells and detaches them. These cells are placed in a small labelled tube and sent to the genetics laboratory. The embryo is then vitrified while awaiting the results, which generally take a few weeks.

This procedure requires great dexterity and perfect traceability, as each sample must match its embryo without error.

The results indicate, for each embryo analysed, whether or not it is affected by the disease being tested for, or whether it has a chromosomal abnormality, depending on the test performed. Some results may be uninterpretable, and a repeat test is not always possible. The geneticist and the doctor explain the results and help you decide which embryo to transfer. Sometimes no transferable embryo is available, which is an ordeal that requires support.

The biopsy takes cells from the outer layer of the blastocyst, the trophectoderm, and not from the inner cell mass, which will form the baby. This limits the impact on the embryo's development. The cells of the outer layer generally reflect the genetic make-up of the whole embryo, but not always, particularly in cases of mosaicism. This is one of the reasons why the test is never infallible.

The exact indications and conditions are set by law; the centre and the geneticist will inform you of what is possible in your situation.

Before considering preimplantation genetic testing, the couple meets a geneticist. The geneticist explains the disease in question, the risk of transmission, the feasibility of testing, its limitations and the alternatives, such as prenatal diagnosis during a natural pregnancy. They also explain what the test may reveal beyond the question asked and how this information will be handled. This counselling enables the couple to make an informed decision in accordance with the law.

Preimplantation genetic testing does not guarantee a pregnancy: it does not create new embryos, and some of the embryos tested may turn out to be affected or uninterpretable. It only detects the abnormalities being tested for, and an error, although rare, remains possible due to the small number of cells analysed and mosaicism. This is why confirmatory prenatal diagnosis may be offered during pregnancy. The cost of testing is added to that of IVF.

Genetic testing may reveal that an embryo is mosaic, meaning it contains both normal cells and cells with an abnormal number of chromosomes. This result is difficult to interpret: some mosaic embryos lead to pregnancies and healthy children, but their chances are lower on average. The decision whether or not to transfer a mosaic embryo is made with a geneticist, depending on the type of abnormality and the couple's situation.

Research is under way into methods of genetic testing of the embryo without biopsy, using DNA released into the culture medium or the blastocyst cavity. These approaches could reduce handling in future. They currently remain experimental or under evaluation, and their reliability does not yet match that of biopsy. They are not offered routinely.

A high-quality IVF laboratory operates under a quality management system: written procedures for each step, regular training and evaluation of embryologists, checks on equipment and media, recording of temperatures, gases and alarms, incident management, and internal and external audits. Many laboratories follow recognised standards and take part in external quality control programmes.

The laboratory also tracks performance indicators: fertilisation rates, blastocyst development rates, survival after warming and pregnancy rates. Monitoring them makes it possible to detect any problem quickly and improve practices.

In addition to their internal controls, many laboratories take part in external quality assessment programmes: for example, they receive samples or embryo images to analyse, and their results are compared with those of other laboratories. These programmes make it possible to check the accuracy of assessments, such as semen analyses or embryo grading, and to detect any drift. It is an indicator of reliability that you can ask the centre about.

In Switzerland, a cantonal licence is mandatory to practise medically assisted reproduction and to store gametes and embryos. In addition, some laboratories choose accreditation under international quality standards, which requires a documented system and regular audits. These steps do not in themselves guarantee a pregnancy, but they demonstrate a commitment to quality and safety.

Despite all precautions, incidents can occur: equipment failure, handling error, storage problem. Laboratories have procedures to react immediately, limit the consequences, inform the couples concerned and analyse the causes to prevent recurrence. Serious incidents are reported to the authorities. Transparency in these situations is one of the centres' obligations.

These indicators also depend on the patients treated; they are mainly used for internal monitoring and comparison with benchmarks.

The results published by a centre can be expressed in different ways: fertilisation, blastocyst, implantation, pregnancy per transfer or per cycle, and birth rates. To compare, you need to check that the same indicators are being compared, for similar age groups. A high pregnancy rate per transfer may hide a low number of transfers per cycle. Ask the centre for its results by age group and the definitions used.

A good laboratory is not recognised by having the latest equipment or the longest list of options, but by the stability of its culture conditions, the experience and training of its embryologists, the rigour of its procedures, the quality of its traceability system, the consistency of its results and the clarity of its explanations. A laboratory that acknowledges the limits of its techniques and informs you honestly deserves your trust.

Clinical embryologists generally have a university degree in biology or medicine, supplemented by specialist training in clinical embryology and extensive practical experience. Procedures such as ICSI, embryo biopsy and vitrification require gradual learning and regular assessment. Teams attend conferences and continuing education to keep up with rapidly evolving techniques.

A successful IVF cycle relies on close coordination between the clinical side and the laboratory. The doctor informs the laboratory of the number of follicles and the time of the trigger; the laboratory plans the egg collection, fertilisation and culture; and the two discuss the stage and day of transfer. After each cycle, they analyse the results together. This collaboration, often invisible to couples, is essential to the quality of care.

All information about your gametes and embryos is covered by medical confidentiality. Samples are identified securely, and only the professionals involved in your treatment have access to your data. Information sent to the national registry is anonymised. For sperm donation, donor data are kept by the authorities in accordance with the law.

In Switzerland, the law on medically assisted reproduction also governs laboratory work: a maximum of twelve embryos developed per treatment cycle, the couple's written consent for freezing and storage, a limited storage period, a ban on sex selection without a medical reason, strict conditions for preimplantation genetic testing, and a ban on embryo donation and on the use of gametes after death. The laboratory must keep a precise register and submit statistical data. These rules aim to protect couples, embryos and the welfare of the child.

In Swiss laboratories, embryos are handled with great respect, in keeping with the spirit of the law, which protects human dignity from the earliest stages of life. They are only created as part of a plan to have a child, in limited numbers, and their fate always depends on the couple's consent. Embryologists know what each embryo represents for the future parents, and this awareness guides every one of their actions, from the first day of culture to transfer or storage. This care is also reflected in the way couples are informed, with tact and honesty, at every stage of their embryos' development, whether encouraging or disappointing.

For married couples using donor sperm, the laboratory works with straws of frozen sperm from a licensed bank. Donors have been selected and tested according to strict medical criteria, and their sperm is quarantined before use. On the day of insemination or fertilisation, the straw is thawed and the sperm prepared, then used in the same way as a partner's. Information about the donor is kept in accordance with the law, which guarantees the child the right to know their origins at the age of 18.

Technically, the laboratory could fertilise eggs from a donor, as it does with the patient's own eggs. But egg donation is currently prohibited in Switzerland, whereas sperm donation is permitted. A change in the law is under discussion. Couples concerned can ask their centre about developments in the legislation. In the meantime, freezing one's own eggs at a younger age remains the option that allows better-quality eggs to be used later.

Under the microscope, nothing reveals the sex of an embryo. Only genetic testing could determine it, but Swiss law prohibits choosing the sex of the child, except to avoid the transmission of a serious sex-linked disease. During preimplantation genetic testing, information on sex is not used to select embryos outside this indication.

Before the cycle, the couple signs consent forms for the laboratory procedures: fertilisation technique, number of embryos developed, freezing and storage period, and possibly preimplantation genetic testing. These documents also specify what happens to the embryos in different situations. Read them carefully, ask the embryologist or doctor any questions, and keep a copy.

Good-quality embryos that are not transferred are vitrified for later transfers, with the couple's consent. They often allow one or more additional transfers without new stimulation. When the plan to have a child has been achieved or abandoned, or at the end of the legal storage period, the couple may decide to have them destroyed or, with their consent, used for research, under the law on embryonic stem cell research. Donation to another couple is prohibited in Switzerland.

Deciding what will happen to your frozen embryos once your plan to have a child has been achieved or abandoned is often difficult. Some couples feel a strong attachment to these embryos, while others see them primarily as cells. In Switzerland, the options are limited by law: continued storage within the legal limits, destruction, or donation to research with consent. Take the time to talk about it together, and do not hesitate to ask the centre's psychologist for help. There is no right or wrong decision, only the one that is right for you.

As long as your embryos are in storage, the centre must be able to reach you: inform it of any change of address, telephone number or family situation. You will receive reminders before storage deadlines and annual invoices. Keep your consent forms and reports, which specify the number of embryos, their stage and their freezing date.

Embryo research is strictly regulated in Switzerland. Only surplus embryos from IVF that can no longer be used for a plan to have a child may be used, with the couple's free and informed consent, mainly to obtain embryonic stem cells, under a specific law and subject to oversight. Creating embryos for research purposes is prohibited. The couple is never obliged to consent to this use.

Laboratory work raises ethical questions that Swiss law regulates: the status of the embryo, the number of embryos created, selection during preimplantation genetic testing, the fate of surplus embryos, and research. The limit of twelve embryos developed per cycle aims to avoid creating a large number of unused embryos. Couples may also face personal choices, for example regarding the fate of their frozen embryos. Teams respect everyone's beliefs and can refer couples for psychological or ethical counselling.

Some couples have personal, philosophical or religious beliefs about the creation and freezing of embryos. It is possible to discuss these with the team to adapt the treatment: for example, limiting the number of eggs fertilised to avoid surplus embryos, sometimes at the cost of reduced chances, or opting to freeze eggs rather than embryos. These choices are discussed before the cycle so that they can be included in the consent forms.

Swiss centres submit their data to a national registry, which tracks the activity and results of reproductive medicine: number of cycles, techniques used, pregnancies, births and complications. These statistics make it possible to monitor the quality of practice, inform the public and the authorities, and compare trends in results over the years. The data submitted are anonymised.

On the day of transfer, the embryologist selects the embryo according to the agreed criteria, checks its condition, places it in a transfer medium and loads it into a soft catheter in a very small volume of fluid. They bring the catheter to the doctor, who deposits it in the uterus under ultrasound guidance. The embryologist then examines the catheter under the microscope to confirm that the embryo has been deposited. The whole sequence is coordinated to limit the time spent outside the incubator.

Many laboratories offer to give the couple a photo of the transferred embryo, taken under the microscope just before the transfer. For some couples, this image is a first connection with their future child; others prefer not to receive it, for fear of being too affected if the cycle fails. Both attitudes are legitimate. If you would like a photo, ask for it in advance. Some laboratories equipped with camera incubators can even offer a short sequence showing the embryo's development.

In many centres, the embryologist meets the couple at the time of transfer to explain the choice of embryo, sometimes show an image on a screen and answer questions. This often moving moment puts a face to the laboratory's work. Do not hesitate to ask to speak to the embryologist at other points in the process, particularly after an unsuccessful cycle.

Once placed in the uterus, the blastocyst continues to develop for one to two days, hatches from its shell and then attaches to the uterine lining. The cells of its outer layer penetrate the lining and begin to produce the pregnancy hormone, detectable in the blood a few days later. Implantation depends both on the quality of the embryo and on the receptivity of the uterus, which is only optimal for a short period.

Even with a very good-quality embryo, implantation is not guaranteed. Some embryos, including chromosomally normal ones, do not implant, for reasons that are not always understood.

Once the pregnancy is confirmed, the laboratory is no longer in the foreground, but it remains linked to your story: it stores any surplus embryos and the information about your cycle. Remember to inform the centre of the outcome of the pregnancy and the birth; this information contributes to the statistics and helps teams evaluate their practices. Many embryologists are touched to receive news from the families they have helped to build, sometimes years later, with a photo of the child.

Implantation relies on a genuine biological dialogue between the embryo and the uterine lining. The embryo sends signals, the lining responds by changing to receive it, and immune cells take part in this exchange. This dialogue is only possible during a short period of the cycle, called the implantation window. Research is trying to better understand these mechanisms, which explain why good-quality embryos do not always implant. For now, few tests can reliably assess this dialogue in routine practice.

As soon as the embryo begins to implant, the cells of its outer layer produce the pregnancy hormone, which passes into the mother's blood. Its level rises rapidly, roughly doubling every two days in the early stages of an ongoing pregnancy. This is the hormone measured by the blood test carried out after the transfer. An insufficient rise may indicate a pregnancy that is not developing normally, hence the value of repeated checks.

Several million children worldwide have been born thanks to in vitro fertilisation, and follow-up studies show that the vast majority are healthy and develop normally. Slight differences have been observed for certain parameters, such as birth weight or prematurity, largely explained by multiple pregnancies and by the parents' infertility itself. Researchers are also studying the possible influence of culture conditions on the expression of the embryo's genes, without any significant consequences for children's health having been demonstrated.

Even when only one embryo is transferred, a twin pregnancy remains possible, though rare: the embryo may split in two and produce identical twins. This phenomenon is slightly more common after extended culture or certain procedures, but it remains rare. Single embryo transfer nevertheless greatly reduces the risk of multiple pregnancy compared with transferring two embryos.

When several good-quality embryos fail to implant, this is referred to as repeated implantation failure. The laboratory and the doctor then review the entire process: egg and embryo quality, fertilisation technique, culture conditions and, above all, factors related to the uterus and age. Further examinations of the uterus, chromosomal analysis of the embryos in the situations provided for by law, or other approaches may be discussed. Be wary of expensive treatments offered without solid evidence.

A fresh transfer takes place during the stimulation cycle, a few days after egg collection. A frozen embryo transfer takes place in a later cycle, in a uterus that has not been exposed to the high hormone doses of stimulation. In many situations, the results are comparable; in some, such as a risk of hyperstimulation, an unfavourable lining or preimplantation genetic testing, freezing all embryos and deferring transfer is preferable. The choice is made case by case.

To implant, the blastocyst must emerge from its shell, the zona pellucida: this is hatching. Assisted hatching involves thinning or opening this shell with a laser to make it easier to emerge. It has been offered for frozen embryos, whose shell may harden, for older women or after failed cycles. Studies do not show a clear benefit for all patients, and its use varies between centres. It may be performed systematically during a biopsy for preimplantation genetic testing.

Before accepting an option, ask about its value in your specific situation, the studies that support it and its cost.

After each cycle, the centre can give you a laboratory report. It generally indicates the number of eggs retrieved, the number of mature eggs, the fertilisation technique, the number of eggs normally fertilised, the embryos' progress day by day, their grade, the embryo transferred and the number of embryos vitrified with their stage and grade.

This information helps identify where any difficulties lie: few eggs, a low maturity rate, insufficient fertilisation, developmental arrest or implantation. It guides adjustments for a subsequent cycle. Ask the embryologist or doctor to explain it to you.

These figures are only an example: every cycle is different, and the proportions vary greatly depending on age and situation.

• How many eggs were mature, and how many were fertilised?
• Why did you choose conventional IVF or ICSI?
• How did the embryos develop day by day?
• What do our embryos' grades mean?
• Why did some embryos stop developing?
• How many embryos were vitrified, and at what stage?
• Would a laboratory option be useful for us?
• What would you change in a future cycle?

If you have questions about your laboratory results, particularly after an unsuccessful or disappointing cycle, you can request a meeting with an embryologist in addition to your consultation with the doctor. They can show you how your embryos developed, explain the observations and discuss possible adjustments. Prepare your questions and bring your report.

After a failed cycle, the laboratory's analysis helps to understand what happened. A low number of eggs points to adjusting the stimulation. A low maturity rate may lead to changing the trigger. Fertilisation failure with conventional IVF leads to ICSI being proposed. Frequent embryo arrest, especially with age, suggests chromosomal abnormalities. Good-quality embryos that do not implant point towards the uterus or other factors. This analysis is carried out as a team, by the doctor and the embryologist.

These indices are for guidance only and vary between centres. IVF laboratory procedures are paid for by the couple. Details are on our page in vitro fertilisation prices.

In Switzerland, basic health insurance does not cover in vitro fertilisation or the related laboratory procedures: fertilisation, ICSI, culture, freezing, storage and preimplantation genetic testing. Some supplementary insurance policies may contribute to part of these costs, depending on the contract. On the other hand, diagnostic tests such as semen analysis are generally covered when used for diagnosis. Check with your insurers before starting.

To estimate the budget, add up the laboratory cost of a complete cycle, embryo vitrification, the expected annual storage and any possible frozen embryo transfers. Add any options, accepting only those with a demonstrated benefit for you. Compare with the clinical cost and medication to get an overall picture. Planning ahead reduces financial stress, which is often significant during the process.

The cost of laboratory procedures reflects the investment required: premises with filtered air, high-precision equipment, incubators, micromanipulators, nitrogen tanks and monitoring systems, single-use media and consumables, quality controls and, above all, the time of a team of specialised embryologists available every day of the year. In Switzerland, these procedures are not covered by basic health insurance. A detailed quote makes it possible to understand what each item covers.

Two centres may present very different quotes, not only in price but in what they include: all-inclusive package or item-by-item billing, extended culture included or not, number of freezings included, options built in or separate. To compare, work out the total cost of a complete cycle, including one fresh transfer and one frozen embryo transfer, excluding options whose benefit has not been demonstrated in your case.

Price differences between centres depend more on packages, options and medication than on the city. Compare detailed quotes.

Laboratory explanations use technical vocabulary. To understand your results properly, choose a centre where you can communicate in your own language, and ask for written reports. In French-speaking Switzerland, everything takes place in French; in the major German-speaking cities, many centres see patients in French or English; in Ticino, in Italian.

Collecting sperm at home is only possible if the transport time to the laboratory is short, generally less than an hour, at a temperature close to body temperature. If you live far away, plan to produce the sample at the centre or freeze a sample beforehand. For egg collection and transfer, organise your journeys in advance, as the times are set precisely.

• Cantonal licence and laboratory quality system.
• Experience of the embryology team and volume of activity.
• Blastocyst culture and vitrification available.
• Preimplantation genetic testing available if needed.
• Transparency about results and indicators.
• Detailed report provided after each cycle.
• Opportunity to talk with an embryologist.

A quality laboratory is not judged by its options, but by the rigour of its work and the clarity of its explanations.

Every licensed reproductive medicine centre in Switzerland has an IVF laboratory or works with a licensed laboratory. They are found in the major cities of French-speaking Switzerland, such as Geneva, Lausanne, Neuchâtel, Fribourg and Sion, of German-speaking Switzerland, such as Zurich, Basel, Bern, Lucerne, St. Gallen, Aarau and Zug, and in Ticino, in Lugano and Locarno. University hospitals often carry out research in reproductive biology.

• Marie, 32: 14 eggs, 11 mature, conventional IVF, 8 fertilised, 4 blastocysts; one transferred, three vitrified.
• Sandra, 38: 7 eggs, ICSI, 5 fertilised, 2 blastocysts; one transferred, the other vitrified.
• Clara, 35, severely impaired sperm: ICSI with testicular sperm, 3 blastocysts.
• Ana, 42: 4 eggs, 3 fertilised, no blastocysts; discussion of chances with the doctor.
• Julie, 30, couple carrying a genetic disease: 6 blastocysts biopsied, 3 unaffected vitrified.
• Léa, 34: fertilisation failure with conventional IVF in the first cycle, successful ICSI in the second.

• Day 0, 8 a.m.: egg collection, eleven eggs found in the follicular fluid.
• Day 0, 10 a.m.: sperm collection and preparation, satisfactory motility.
• Day 0, 2 p.m.: denudation, nine mature eggs, ICSI performed.
• Day 1: seven normal fertilisations, one egg with three nuclei discarded.
• Day 3: six embryos of six to eight cells.
• Day 5: two good-quality blastocysts, one forming.
• Day 5, 11 a.m.: transfer of one blastocyst, catheter check.
• Day 6: two blastocysts vitrified.
• Report given to the couple.

• Preparation of the uterus with hormone treatment, ultrasound check of the lining.
• Transfer day, 8 a.m.: warming of the chosen blastocyst.
• Two hours later: survival confirmed, re-expansion of the cavity.
• Transfer under ultrasound guidance, catheter checked under the microscope.
• Nine days later: blood test for pregnancy.

• Genetic counselling, preparation of the test specific to the family disease.
• IVF with ICSI, culture to the blastocyst stage.
• Days 5 and 6: biopsy of four blastocysts, each one vitrified.
• Three weeks later: two unaffected embryos.
• Next cycle: warming and transfer of one unaffected embryo.

• "The more eggs, the safer": quality matters as much as quantity.
• "A highly graded embryo always leads to a pregnancy": the grade is a probability.
• "ICSI is always better": it is only useful for certain indications.
• "Freezing damages embryos": vitrification preserves them very well.
• "The laboratory can correct a poor-quality egg": it can only optimise the conditions.
• "All options improve the chances": many have not demonstrated their value for everyone.

• Clinical embryologist: specialist working in the IVF laboratory.
• Cumulus: cells surrounding the egg.
• Zona pellucida: outer shell of the egg and embryo.
• Capacitation: maturation of the sperm that makes it capable of fertilising.
• Zygote: fertilised egg.
• Morula: compacted embryo on day four.
• Blastocyst: embryo of five to six days.
• Vitrification: ultra-rapid freezing.
• Warming: thawing.
• Mosaic: embryo with both normal and abnormal cells.
• Hatching: emergence of the blastocyst from its shell.

Between egg collection and transfer, many couples anxiously await news from the laboratory: how many eggs have been fertilised, how many embryos are developing, how many will reach the blastocyst stage. Each call can bring relief or disappointment. It is common for the number of embryos to decrease as the days go by; this is a normal process and does not necessarily predict the outcome of the cycle.

Preparing your questions, noting down the information given and then discussing it with the doctor helps you get through these days. Teams know that this period is difficult and take the time to explain.

As the laboratory calls come in, numbers take on great importance: the number of eggs, fertilisations, embryos and blastocysts. Each decrease can feel like a loss. It is helpful to remember that these numbers describe a normal biological process, and that a single good-quality embryo is enough for a pregnancy. Couples who have received clear information about this process before the cycle often cope better with this period.

Some couples like to keep their loved ones informed day by day, while others prefer to keep this information to themselves until the pregnancy test. There is no right answer. Sharing can bring support, but also difficult questions if the news is bad. Decide together what you want to say, and to whom.

• Ask when the laboratory will call you, so you can plan your days.
• Write down the information given and your questions.
• Do not compare your numbers with those of other couples.
• Remember that a decrease in the number of embryos over the days is normal.
• Ask for the written report of the cycle.
• Talk about your emotions with your partner or a professional.

• "What if my embryos were mixed up with another couple's?" Double checks and traceability make this risk exceptional.
• "Can my frozen embryos be lost?" Tanks are monitored continuously, with alarms and back-up procedures.
• "Does the laboratory choose the sex?" No, this is prohibited without a medical reason.
• "Why do I have so few embryos?" This is often linked to age and egg quality, not the laboratory.
• "Would a paid option increase our chances?" Not always; ask for the evidence.

Entrusting your eggs, sperm and embryos to a laboratory requires trust. This trust is built through clear explanations, a detailed report, the opportunity to talk with the embryologists and transparency about results. Asking questions is not a sign of mistrust, but a way of taking an active part in your journey. Laboratory teams generally appreciate couples who want to understand.

Each partner often experiences the laboratory days differently: one may cling to the numbers, the other may prefer not to know too much. It helps to talk about it, to decide together who takes the calls, and to share your emotions without judgement. This time, when the couple can only wait, can also be an opportunity to reconnect, away from appointments and treatments.

A good laboratory communicates clearly and honestly: it explains its choices, the results of each step, the uncertainties and the reasons for any developmental arrest. It provides a written report and is willing to answer questions. This transparency helps couples understand their journey, take part in decisions and maintain trust, even when difficulties arise.

Laboratory advances have played a major role in improving IVF results over recent decades: ICSI made it possible to treat severe male infertility, blastocyst culture improved embryo selection, and vitrification made single embryo transfer possible without loss of cumulative chances. Current studies focus on embryo assessment, genetic testing and artificial intelligence, with promising results that have yet to be confirmed.

Research in reproductive biology is exploring many avenues: a better understanding of egg quality, culture media closer to natural conditions, automated embryo assessment, less invasive genetic testing, improved implantation, laboratory maturation of eggs and fertility preservation in children. Some of these avenues could improve results in the coming years; others will remain experimental. Swiss centres take part in this research, within the strict framework of the law.

New laboratory techniques are often presented with enthusiasm before their benefit has been demonstrated by robust studies. An innovation is not necessarily progress for all couples. Professional societies regularly evaluate the options offered and recommend using them only when their value has been proven. A reputable laboratory adopts innovations with discernment and explains honestly what they can offer you.

• The laboratory takes care of the gametes and embryos between egg collection and transfer.
• Fertilisation is carried out by conventional IVF or ICSI depending on the situation.
• Embryos are cultured for up to five or six days and assessed under the microscope.
• Assessment is a probability, not a certainty.
• Vitrification makes it possible to store embryos and transfer one embryo at a time.
• Egg quality, which is linked to age, remains the decisive factor.
• Swiss law regulates the number of embryos, their storage and genetic testing.

• Choosing between conventional IVF and ICSI, depending on the sperm and history.
• Deciding on the transfer stage: day three or blastocyst.
• Deciding on the number of embryos to transfer, usually one.
• Consenting to vitrification of surplus embryos.
• Considering preimplantation genetic testing or not, in the cases provided for by law.
• Accepting or declining a laboratory option.
• Deciding on the eventual fate of the embryos.

These decisions are made with the doctor and the embryologist, who explain the advantages and limitations of each choice.

• Focusing solely on the number of eggs.
• Interpreting embryo grades as certainties.
• Accepting all paid options without discussing their value.
• Not asking for the laboratory report.
• Comparing your numbers with those of other couples without taking age into account.
• Forgetting to renew embryo storage.

• Signing consent forms and blood tests.
• Sperm collection and egg collection on the same day.
• Gamete preparation and fertilisation.
• Fertilisation check the following day.
• Culture and daily assessment of the embryos.
• Transfer of one embryo, vitrification of the others.
• Report given to the couple.
• Warming and transfer of a frozen embryo in a later cycle.

Medespoir Suisse helps you understand the laboratory stages, prepare your questions for the embryologist and the doctor, and find a licensed reproductive medicine centre in your region and your language. Describe your situation to us in complete confidence; we will refer you free of charge and without obligation.

If you are considering in vitro fertilisation, or if you are already undergoing treatment and would like to better understand the laboratory's work, talking with a reproductive medicine centre is the best way to start. Describe your situation, your age, how long you have been trying for a child and the tests already carried out. Medespoir Suisse can refer you to a licensed centre in your region and your language, confidentially, free of charge and without obligation.

• Your age and your partner's age.
• How long you have been trying for a child.
• Tests already carried out, notably semen analysis and ovarian reserve.
• Treatments already tried.
• Your questions about the laboratory and techniques.
• Your preferred language.

This information enables the centre to offer you a suitable appointment quickly.

The laboratory is the discreet heart of in vitro fertilisation. Day after day, embryologists oversee the meeting of the gametes and the embryo's first steps with rigour, precision and care. Understanding their work helps couples cope better with the process, interpret results and ask the right questions. To find out more, see our IVF and assisted reproduction guide and our page on the IVF journey in Switzerland.

Your IVF journey passes through the hands of many people, some of whom you may never see. In the laboratory, embryologists watch over your eggs, sperm and embryos with constant attention. Do not hesitate to ask them questions, request explanations and share your concerns: understanding what happens in the laboratory often helps you face the waiting and the decisions with greater peace of mind.

If you are about to start IVF, take the time to meet the laboratory team or find out how it works, ask how you will be kept informed at each step, and prepare your questions. Understanding the laboratory's work often turns an anxious wait into a better-managed stage, and allows you to take a full part in the decisions concerning your future embryos.

In vitro fertilisation relies on precise, rigorous and regulated laboratory work. Conventional IVF or ICSI, blastocyst culture, embryo assessment and vitrification are now proven techniques. They cannot compensate for the age-related decline in egg quality, but they give embryos the best conditions to reveal their potential. Choosing a centre with a high-quality laboratory, asking for explanations and keeping realistic expectations are the keys to an informed journey.

At the end of this journey through the heart of the laboratory, one idea stands out: every step, from sperm preparation to vitrification, is designed to give your gametes and embryos the best possible conditions. Embryologists cannot change biology, but they put their expertise at the service of your plans, with rigour and respect. Understanding their work also helps you live your own journey better.

Budget

Price differences between cities and cantons, the breakdown of the quote and ways to save are detailed on our page In vitro fertilisation: prices in Switzerland.

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Answers to the most frequently asked questions about the work of the in vitro fertilisation laboratory in Switzerland.

The IVF laboratory

What does the IVF laboratory do? It prepares the sperm, identifies the eggs in the fluid collected, performs fertilisation, cultures and assesses the embryos, prepares the embryo for transfer, vitrifies surplus embryos and gametes, and stores everything under controlled and traceable conditions.

Who works in the laboratory? Clinical embryologists, also known as reproductive biologists, assisted by laboratory technicians. They work closely with the centre's gynaecologists.

Is the laboratory regulated? Yes. In Switzerland, reproductive medicine centres and their laboratories must hold a cantonal licence, meet quality requirements and submit their data. Many laboratories also follow recognised quality standards and undergo external controls.

Why are laboratory conditions so important? Eggs and embryos are extremely sensitive to temperature, acidity, light, air quality and changes in their environment. Laboratories reproduce the conditions of the body as closely as possible and limit any disturbance, which directly influences the chances of success.

How does the laboratory avoid identification errors? Through double-check procedures at every step, labelling of every dish and tube, and often electronic identification systems. Every handling step is traced, from gamete collection to transfer or freezing.

Can I visit the laboratory? For hygiene and safety reasons, access is restricted. However, the embryologists can explain their work, show images and sometimes a photo of your embryos.

Does the laboratory work at weekends? Yes, embryos develop every day, and egg collections and transfers follow the biological rhythm. Laboratories therefore also operate at weekends and on public holidays as required.

Why do results vary from one laboratory to another? Equipment, culture media, procedures, the embryologists' experience and the profile of the patients treated all influence results. That is why it is useful to know a centre's results by age group.

What is the difference between an embryologist and a gynaecologist? The gynaecologist looks after the patient: stimulation, egg collection, transfer, follow-up. The clinical embryologist looks after the gametes and embryos in the laboratory. The two work closely together at every step.

Does the laboratory use products of animal origin? Current culture media are defined and controlled medical products designed for human use. Their composition is regulated and traceable.

What happens in the event of a breakdown? Laboratories have back-up systems for electricity, gases and alarms, as well as emergency procedures. The nitrogen tanks are monitored continuously.

Sperm

How is sperm collected on the day of egg retrieval? By masturbation, in a dedicated room at the centre, or sometimes at home with a short transport time, after a few days of abstinence. If difficulties are expected, the sperm can be frozen in advance.

How does the laboratory prepare the sperm? The semen is washed and processed, often by density gradient centrifugation or swim-up, to separate motile, well-formed sperm from the seminal fluid, cells and debris. The result is a small quantity of concentrated, selected sperm.

What happens if there is no sperm? If no sperm is found on the day of egg retrieval, the biologists search the sample meticulously. If the absence is already known, surgical sperm retrieval from the testicle can be carried out in advance or on the same day. See our page on testicular biopsy.

Can frozen sperm be used? Yes. Frozen sperm from the partner, or from a donor for eligible married couples, is thawed on the day of fertilisation. Results are generally good, especially with ICSI.

What is sperm DNA fragmentation? It is a measure of breaks in the DNA of sperm. Some centres offer it after repeated failures or miscarriages. Its value in guiding treatment is still debated; ask your doctor whether it would be useful in your situation.

Are sperm selected on the basis of their appearance? In conventional IVF, selection is natural, among the prepared sperm. In ICSI, the biologist chooses a motile sperm of normal shape under the microscope. More advanced selection techniques exist, but their benefit has not been demonstrated for everyone.

Is abstinence needed before collection? Abstinence of two to five days is generally recommended, according to the centre's instructions, to obtain a good-quality sample.

Can the partner freeze his sperm in advance? Yes, if difficulties are foreseeable on the day of egg retrieval, if he expects to be away or in case of significant stress. The frozen sperm is thawed on the day of fertilisation.

Can sperm retrieved from the testicle be used? Yes, with ICSI. They are often few in number and have low motility, but a single sperm is enough for each egg. They can be used fresh or frozen.

Eggs

How are eggs found after retrieval? The fluid aspirated from each follicle is immediately examined under the microscope by the biologist, who identifies the eggs surrounded by their cells. They are then placed in culture medium and in an incubator.

Does every follicle contain an egg? No. Some follicles seen on ultrasound contain no egg, or an egg that is not retrieved. This is why the number of eggs is often lower than the number of follicles.

What is a mature egg? It is an egg that has completed a stage of its maturation and can be fertilised. At retrieval, some of the eggs may be immature. Only mature eggs are used in ICSI.

Can immature eggs be matured in the laboratory? In vitro maturation is a technique that allows eggs retrieved immature to mature in the laboratory. It is used in specific situations, such as some fertility preservation cases, but its results are lower than those obtained with mature eggs.

Can egg quality be seen under the microscope? Partly. Some visible abnormalities can be noted, but the appearance of an egg cannot predict with certainty its ability to produce an embryo. Quality depends above all on the woman's age.

Why does egg quality decline with age? Over the years, eggs accumulate more errors in the distribution of chromosomes during their maturation. The resulting embryos more often have an abnormal number of chromosomes, which reduces the chances of implantation and increases the risk of miscarriage.

How many eggs are collected on average? The number varies greatly depending on age, ovarian reserve and response to stimulation, from just a few to more than fifteen. A moderate number of good-quality eggs is often better than a large number of lower-quality eggs.

Can eggs be frozen on the day of retrieval? Yes, mature eggs can be vitrified without being fertilised, for example for fertility preservation or if sperm is not available on the day.

Is the egg damaged by retrieval? Retrieval, performed with a fine needle under ultrasound guidance, does not generally damage the eggs. Laboratory handling is designed to protect them.

Fertilisation

How does fertilisation work in conventional IVF? Each egg is placed in a drop of culture medium with several tens of thousands of prepared sperm. One of them naturally penetrates the egg. The next day, the biologist checks whether fertilisation has taken place.

How is ICSI performed? The biologist removes the cells surrounding the egg, holds it in place with a pipette, chooses a sperm, immobilises it, then injects it directly into the egg with a very fine micropipette, under a microscope fitted with micromanipulators.

When is ICSI chosen rather than conventional IVF? In cases of male infertility, sperm retrieved from the testicle, failed fertilisation in a previous IVF cycle, frozen eggs or preimplantation genetic testing. The choice is discussed with the doctor and the biologist.

How do we know an egg has been fertilised? Around sixteen to twenty hours after insemination, the biologist sees two small nuclei inside the egg, one from the egg and the other from the sperm. This is the sign of normal fertilisation.

What proportion of eggs are fertilised? On average, most mature eggs are fertilised, but the proportion varies greatly depending on the quality of the eggs and sperm. It is common for not all of them to be fertilised.

What is abnormal fertilisation? Sometimes the egg shows one or three nuclei instead of two, a sign of abnormal fertilisation. These eggs are generally not used, as the resulting embryos would have abnormal genetic material.

What happens if fertilisation fails completely? The biologist and the doctor analyse the possible cause. In the next cycle, ICSI is generally offered if conventional IVF had been used. Other adjustments may be discussed.

Can conventional IVF and ICSI be combined? Yes, in specific situations some centres split the eggs between the two techniques, to maximise the chances of fertilisation and better understand the results.

Does ICSI carry risks for the child? The vast majority of children born after ICSI are healthy. Some studies suggest a slight increase in certain risks, partly linked to male infertility itself. The doctor will inform you of the current data.

Why are some eggs not fertilised? They may be immature or of insufficient quality, or the sperm may fail to penetrate them. Even with ICSI, fertilisation is not guaranteed.

Embryo culture

Where are embryos cultured? In incubators that maintain a temperature close to body temperature, a controlled gas atmosphere and suitable humidity. The embryos are bathed in culture media that provide the elements they need to develop.

How does an embryo develop day by day? On day two, it has around two to four cells; on day three, around six to eight; on day four, the cells compact; on day five or six, it becomes a blastocyst, with a cavity, an outer layer and a cluster of cells that will form the foetus.

What is a blastocyst? It is a five- to six-day-old embryo made up of more than a hundred cells, with a fluid-filled cavity, an outer layer that will form the placenta and an inner cell mass that will form the baby. This is the stage at which the embryo naturally implants in the uterus.

Why culture to the blastocyst stage? Progression to the blastocyst stage makes it possible to select the embryos with the best potential, as some embryos stop developing before this stage. Transferring a blastocyst often offers better chances per transfer.

Do all embryos reach the blastocyst stage? No, some stop along the way, often because of chromosomal abnormalities or insufficient potential. This is a natural selection process that also occurs in natural conception.

What is a time-lapse incubator? Some incubators take regular images of the embryos without removing them from the incubator, making it possible to monitor their development continuously. They reduce handling and provide additional information, but their benefit on birth rates has not been clearly demonstrated.

Are embryos handled often? As little as possible. Observations are quick and scheduled. Each removal from the incubator is kept to a minimum to avoid variations in temperature and atmosphere.

Does the culture medium influence the embryos? Yes, culture media are designed to meet the needs of embryos at each stage. Laboratories choose validated media and check their quality.

Why do some embryos stop developing? Most often because of chromosomal abnormalities or insufficient potential, sometimes linked to egg quality. This natural sorting also occurs in natural conception.

Is transfer always done on day five? Not always. Depending on the number and progress of the embryos, transfer can be done on day three or at the blastocyst stage. The biologist and the doctor choose the most suitable time.

Embryo assessment

How does the biologist assess an embryo? They look at the number and regularity of the cells, the presence of fragments, the speed of development and, at the blastocyst stage, the expansion of the cavity and the quality of the inner cell mass and the outer layer. These criteria lead to a grading.

What do blastocyst grades mean? Blastocysts are often described by a number indicating their degree of expansion and two letters describing the quality of the inner cell mass and the outer layer. These grades help choose which embryo to transfer first, but do not guarantee a pregnancy.

Can a lower-quality embryo lead to a pregnancy? Yes. Assessment criteria are indicators of probability, not certainties. Embryos graded as average lead to pregnancies, and embryos graded as excellent may fail to implant.

Does embryo quality depend on the man or the woman? On both, but the egg plays a major role in the first few days, which explains the importance of the woman's age. The sperm also plays a part, particularly from day three onwards.

Can you see a photo of your embryo? Often, yes. Many laboratories provide a photo of the transferred embryo. Ask for one if it matters to you.

Can the sex of the embryo be seen? No, it cannot be seen under the microscope. It can only be determined by genetic testing, which is permitted in Switzerland only to avoid a serious sex-linked disease.

How many embryos are obtained on average? The number varies widely. From a given number of eggs, only some produce embryos, and only some of those reach the blastocyst stage. The biologist keeps you informed of progress day by day.

Are embryos ranked in order of transfer? Yes, the embryo judged to have the best potential is generally transferred first, with the others frozen in order of preference for subsequent transfers.

Freezing and storage

What is vitrification? It is ultra-rapid freezing: after treatment with cryoprotectants, the embryo or egg is plunged directly into liquid nitrogen, at around minus one hundred and ninety-six degrees. The speed prevents the formation of ice crystals that would damage the cells.

Do embryos survive thawing? With vitrification, the vast majority of embryos and blastocysts survive thawing and retain their potential. Pregnancy rates after frozen embryo transfer are comparable to those of fresh transfers in many situations.

How long can embryos be stored? Swiss law limits the storage period, with the possibility of extension on request. The centre will inform you of the applicable time limits and the steps to take.

Do eggs freeze as well as embryos? Thanks to vitrification, eggs now freeze well, with good survival rates. Their chance of leading to a pregnancy depends mainly on age at the time of freezing and the number of eggs stored.

How are frozen samples stored? In liquid nitrogen tanks, monitored continuously by alarms, with safety procedures to prevent any loss. Each sample is identified and recorded.

What happens to embryos at the end of the storage period? They are destroyed or, with the couple's consent, may be used for research in accordance with the law. Donating embryos to another couple is prohibited in Switzerland.

Can embryos be transferred to another centre? Yes, frozen embryos can be transported between authorised centres following secure procedures. Check with both centres.

Can an embryo be frozen on day three? Yes, embryos can be vitrified on day three or at the blastocyst stage. Most laboratories now prefer to freeze blastocysts.

Does freezing affect children's health? The available data on children born after frozen embryo transfer are reassuring. Certain differences, such as a slightly higher birth weight, are being studied.

Embryo genetics

What is preimplantation genetic testing? It is the genetic analysis of a few cells taken from the embryo, usually at the blastocyst stage, before transfer. It makes it possible to identify embryos carrying a serious hereditary disease or an abnormal number of chromosomes.

Is preimplantation genetic testing permitted in Switzerland? Yes, since 2017, under strict conditions: for couples carrying a serious hereditary disease, or when the couple cannot otherwise have a child, within the framework laid down by law. Selecting characteristics without a medical reason is prohibited.

How is the embryo biopsy performed? The biologist removes a few cells from the outer layer of the blastocyst, the layer that will form the placenta, using a laser and a micropipette. The embryo is then vitrified while awaiting the test results.

Does the biopsy damage the embryo? When performed by experienced biologists at the blastocyst stage, according to the available data it does not significantly affect the embryo's potential. It is not without consequences, however, and is only offered when indicated.

Are embryos with chromosomal abnormalities common? Yes, especially with age. A large proportion of embryos, particularly in women over forty, have an abnormal number of chromosomes. This is a major reason for implantation failure and miscarriage.

What is a mosaic embryo? It is an embryo that contains both cells with a normal number of chromosomes and abnormal cells. Its potential is intermediate and its interpretation complex; transferring such an embryo should be discussed with a geneticist.

Does preimplantation genetic testing improve the chances? It avoids transferring embryos affected by a serious disease or a chromosomal abnormality, and may reduce miscarriages in certain situations. It does not increase the number of embryos available, and its value for all couples has not been demonstrated.

Is preimplantation genetic testing one hundred per cent reliable? No, no test is infallible. Prenatal diagnosis during pregnancy may be offered to confirm the results.

Transfer and afterwards

How is the embryo prepared for transfer? The biologist selects the embryo, places it in a suitable medium and loads it into a fine catheter just before transfer. Identity is checked with the couple and the doctor.

Does the laboratory check that the embryo has been deposited? Yes, after the transfer, the biologist examines the catheter under the microscope to make sure the embryo has not remained inside.

What is assisted hatching? It is a technique that thins or opens the embryo's outer shell with a laser to help it hatch and implant. It is used in certain situations, particularly for frozen embryos, but its general benefit has not been demonstrated.

What is embryo glue? It is a transfer medium enriched with a substance intended to promote implantation. Data on its effectiveness are debated; its use varies from centre to centre.

Why is only one embryo transferred? To avoid multiple pregnancies, which carry greater risks for the mother and the babies. The other good-quality embryos are vitrified, which preserves the cumulative chances.

Does the laboratory keep the couple informed? Yes, after retrieval and then as the embryos develop, the centre informs the couple of the number of eggs, fertilisations and embryos and their progress, as well as the embryos frozen.

How long after transfer does the embryo implant? A blastocyst starts to implant around one to two days after transfer, and implantation continues over several days. The pregnancy test is carried out around nine to eleven days after a blastocyst transfer.

Can two embryos be transferred? It is possible in certain situations, after discussion, but single embryo transfer is preferred to limit multiple pregnancies.

What happens to embryos that do not develop? Embryos that stop developing cannot be transferred or frozen. They are disposed of according to the laboratory's rules.

Are frozen embryos used in order? Generally, the embryo judged best is used first, but the choice may take other factors into account, such as the day of freezing or the results of preimplantation genetic testing.

Costs, regulations and centres in Switzerland

Are laboratory procedures reimbursed? No, IVF laboratory procedures (fertilisation, ICSI, culture, freezing and storage) are paid for by the couple in Switzerland, as is IVF as a whole.

How much do laboratory procedures cost? They account for a significant share of the cost of IVF. We express them as relative indices on our prices page. Ask the centre for a quote that itemises each procedure.

Are laboratory options charged separately? Often, yes: for example time-lapse incubators, assisted hatching, embryo glue or certain sperm selection techniques. Ask what evidence supports each option before accepting it.

How many embryos can be developed in Switzerland? The law limits the number of embryos that can be developed per treatment cycle to twelve. Good-quality embryos that are not transferred can be frozen.

How do you choose a centre based on its laboratory? Find out about certifications, the experience of the team of biologists, the techniques available, results by age group and how clearly things are explained. Meeting or talking with a biologist can also help.

Where can you find an IVF laboratory in Switzerland? Every authorised reproductive medicine centre has its own laboratory or works with an authorised laboratory. They can be found in the main cities: Geneva, Lausanne, Bern, Basel, Zurich, Lucerne, St. Gallen, Lugano and others.

Can you speak to a biologist? Yes, most centres allow couples to talk to a biologist, particularly after retrieval or after a failed cycle, to understand the laboratory results.

Can Medespoir advise me? Yes. Describe your situation and the steps you have already taken. We will refer you to an authorised reproductive medicine centre in your region and your language. Free, confidential and with no obligation.

Is the same laboratory used for every stage? Yes, as a rule, the centre's laboratory handles every stage, from gamete preparation to freezing. Certain genetic tests are carried out by specialised partner laboratories.

Do Swiss laboratories use the same techniques? The core techniques (IVF, ICSI, culture to the blastocyst stage and vitrification) are available at every centre. Certain options, such as time-lapse incubators or preimplantation genetic testing, vary from centre to centre.

Can you request a laboratory report? Yes, you can request a detailed report for each cycle: number of eggs, fertilisations and embryos, their progress and the embryos frozen. This is useful for understanding the results and if you decide to change centre.

Is a failed cycle always due to the laboratory? No. Failures are most often linked to egg and embryo quality, and therefore to age and the cause of infertility, or to implantation. Analysis of a failed cycle examines every stage.

Can the laboratory improve egg quality? No, the laboratory cannot improve an egg. It can only provide the best conditions for its potential to be realised.

Is research improving results? Yes, laboratory techniques are progressing steadily, as ICSI and vitrification have shown. Some innovations are promising, others have yet to be evaluated. Centres gradually adopt those that have proven their worth.

Is consent required for laboratory procedures? Yes, after receiving full information, the couple gives written consent to fertilisation, freezing, any preimplantation genetic testing and what happens to the embryos.

Is laboratory data confidential? Yes, it is covered by medical confidentiality. Statistical data sent to the national register are anonymised.

Describe your situation and the steps you have already taken. We will refer you to an authorised reproductive medicine centre in your region and your language. Free, confidential and with no obligation.