In vitro fertilization (also called IVF) consists of reproducing in the laboratory what happens naturally in the fallopian tubes: fertilization and the first stages of embryo development.
The stimulation of the ovaries will allow the development of several follicles each containing an egg. The puncture allows the collection of several mature eggs.
The collected eggs are put in the presence of the spermatozoa outside the human body, in an embryology laboratory.
Two types of IVF exist :
- Conventional IVF simply consists of placing the collected eggs in the presence of the previously treated sperm sample, in a specific nutrient medium. Fertilization takes place according to the natural process but outside the body.
- IVF with ICSI (also called intra-cytoplasmic sperm injection) involves injecting a single sperm inside the egg. Thus the egg and the sperm will have to undergo a treatment beforehand.
If there is fertilization, the early stages of embryo development (a few cell divisions) take place outside the human body and are monitored by the team of embryologists.
Three to six days after fertilization, the embryo is placed back into the woman's uterus, this is called embryo transfer. The embryo will be able to carry out its implantation.
The terms of these particular treatments will be explained in the pre-IVF consultation.
Ovarian stimulation:
Eggs develop inside the ovary, in the follicles. In the natural menstrual cycle, several follicles compete at the onset of menstruation. Only one or two of these follicles will mature about 2 weeks later and will be released when the follicle ruptures (ovulation). Follicles that have not matured stop growing and degenerate. Thus, very few eggs reach the final stage of ovulation in a woman's life.
The purpose of stimulation:
ovarienne en FIV est d’empêcher la dégénérescence de ces follicules en les exposant à une dose suffisante de FSH. En administrant de la FSH sous forme d’injection, on obtient des taux circulants dans le sang plus élevés qui favorisent le développement de follicules multiples et la maturation de plusieurs ovules simultanément. Cette multiplication du recrutement folliculaire, appelée aussi hyperstimulation ovarienne contrôlée, améliore les chances de succès de la FIV en augmentant le nombre d’embryons disponibles.
Triggering of ovulation and programming of the puncture:
When the follicles have reached the desired size and the estrogen levels are sufficient, the final phase of egg maturation is induced by an injection of chorionic gonadotrophic hormone or hCG.
Some properties of the hCG hormone are close to those of LH. Therefore, it is used in in vitro fertilization for the final maturation of the follicles.
Follicular puncture or egg retrieval
The follicular puncture, which makes it possible to collect eggs, is scheduled approximately 35 hours after the injection.
On the morning of the collection, an intravenous catheter will be placed by the nurse in order to administer a relaxant and an analgesic medication.
After performing local anesthesia of the vaginal or paracervical wall, an ultrasound probe (or endovaginal probe) fitted with a guide is introduced into the vagina and the follicles are visualized. A fine needle is introduced through the guide of the vaginal wall and then towards the ovary.
The follicles are punctured one by one. The follicular fluid containing the egg is aspirated and collected in a tube. The intervention is of short duration (15-20 minutes).
The tubes containing the follicular fluid immediately transported to the laboratory where the embryologist determines the number of eggs collected.
After ovarian stimulation, an average of 8 to 10 eggs are recovered. The return home is made after 1 to 2 hours of observation.
Light bleeding (spotting) from the vaginal wall may occur. Do not worry. Talk to your nurse if the bleeding persists or is more abundant. Under no circumstances should you suspend your medication.
Sperm collection and preparation:
On the day of the egg retrieval, the spouse takes a sample of sperm by masturbation, which will be used for fertilization. The sperm could also have previously been cryopreserved.
Whatever its origin, the sperm is analyzed and prepared in the same way. The seminal fluid which limits the fertilizing power of the sperm is eliminated and the most mobile spermatozoa, which are a priori the most fertilizing, are selected.
It is also possible to surgically remove sperm from the testicle or epididymis.
Fertilization or insemination of eggs:
Depending on the type of infertility, fertilization is left to chance (classic IVF) or on the contrary directed (IVF with ICSI).
Classic fertilization:
Three to four hours after the puncture, 50 to 100,000 motile sperm are brought into contact with the ova in a nutrient medium. Contact between sperm and egg lasts about 20 hours.
ICSI or micro-injection (IVF with ICSI):
This technique is used when the male partner has reduced fertility, i.e. when the semen contains too few sperm capable of fertilizing the eggs in conventional IVF.
First, about 2 to 3 hours after the puncture, the eggs are “stripped”, that is to say, freed from the different cell layers that surround them using
The maturity of the eggs is checked under the microscope by the embryologist and only mature and normal-looking eggs can be injected.
At the beginning of the afternoon, the micro-injection is performed: a "normal" sperm is immobilized and then sucked into a micropipette. It is then injected into the cytoplasm of the egg. The pipette perforates the egg and deposits the sperm in the center of the latter.
Only one sperm is needed per egg. The operation is repeated as many times as there are mature eggs available.
Although delicate, ICSI is an effective technique. Indeed, approximately 80% of the eggs obtained by hormonal stimulation are mature and can be injected.
The different stages of the technique can lead to the loss of around 10% of mature eggs. On average more than 70% of the eggs that survive the injection, divide and give rise to embryos that can be implanted in the uterus.
Development and embryo transfer:
Once inseminated or injected, the eggs are placed back in an incubator where the conditions existing in the fallopian tubes are reproduced. The day after the puncture, the eggs are observed under a microscope to determine which ones have been fertilized. A second evaluation takes place, two days after the puncture, during which the exact number and quality of the embryos can be established. At this stage, the embryo has already started its divisions, it is made up of 2 to 4 cells.
Three to six days after egg collection, the embryo is transferred to the uterus. On the 2nd day, the embryos have divided into 2 to 4 cells, on the 3rd day, they have reached the stage of 6 to 8 cells. On the 5th or 6th day, they are at the blastocyst stage.
Transfer is a painless process but can be uncomfortable as it requires a full bladder. This procedure is performed under abdominal ultrasound to clearly visualize the place where your embryo will be transferred.
The embryo is placed in a fine flexible catheter and deposited in the uterine cavity. A single embryo will most often be transferred, in order to reduce the risk of multiple pregnancies and therefore of complications.
The pregnancy test:
About 15 days after the egg retrieval, a pregnancy test carried out by means of a blood test will allow you to know the outcome of the treatment.
- If the test is positive:
If the test is positive, a new blood test will be requested approximately 2 days later to ensure the correct evolution of the pregnancy hormone level. Also, an ultrasound will be scheduled approximately 4 weeks after the transfer to check that the pregnancy is progressing well.
- If the test is negative:
A subsequent consultation with a gynecologist from the center will be scheduled in order to discuss the probable causes of the failure and to consider the consequences of your treatment: transfer of frozen embryos, new attempt, new scheme...
It is advisable to let at least one complete menstrual cycle pass before considering any new attempt. This delay allows recovery both physically and psychologically after the stress and inconvenience generated by the treatment and it allows time to recover from the disappointment caused by the failure of the previous attempt.