IVF literally means "fertilization in a test tube." IVF (in vitro fertilization) is a method to achieve fertilization outside the human body by combining laboratory oocytes of women and the man's sperm. The fertilized eggs that result (embryos) are then placed in the woman's uterus.
The conduct of an IVF cycle involves several stages:
- Ovarian stimulation
- The timing of ovulation
- The follicular puncture
- The collection and preparation of semen
- The development and transfer of embryos
- Cryopreservation of supernumerary embryos
Oocytes grow within ovarian follicles in. In the natural menstrual cycle, several follicles are growing at the beginning of menstruation. Only one or two of these follicles will mature about 2 weeks later and will be released during the follicular rupture (ovulation). Follicles that are not mature stop growing and degenerate. Thus, very few oocytes reach the final stage of ovulation in a woman's life.
The goal of ovarian stimulation in IVF is to prevent the degeneration of the follicles by exposure to a sufficient dose of FSH. Administering of FSH by injection, you get higher circulating levels that support the development of multiple follicles and maturation of several oocytes. This proliferation of follicular recruitment, also known as controlled ovarian hyperstimulation, improves the chances of success of IVF by increasing the number of embryos available
Of ovulation (the timing of ovulation)
When the follicles have reached the desired size and estrogen levels are sufficient, the final phase of maturation of oocytes is induced by an injection of hCG (Choriomon ® Ovitrelle ®, Pregnyl ®). Follicular aspiration (oocyte collection) is scheduled approximately 35 hours after injection.
Under light general anesthesia, an ultrasound probe with a guide is inserted into the vagina and the follicles are identified. A thin needle is inserted through the guide in the vaginal wall and the ovary and the follicles are punctures one by one. The follicular fluid containing the egg is sucked and collected in a tube. The intervention is short (15-20 minutes). During surgery, the tubes containing the follicular fluid are kept at body temperature in an incubator. They are then immediately transported to the laboratory where the biologist determines the number of oocytes harvested. After ovarian stimulation, we get an average of 8 to 10 oocytes. The patient is then transferred into a room where the result of the drain will be communicated in one hour. After 3 to 4 hours of observation, it can go home.
The collection and preparation of semen
On the day of oocyte aspiration, the spouse takes a sample by masturbation semen to be used for fertilization.
In the event of major difficulty of sampling, it is possible to arrange in advance, a cryopreservation of sperm, which can be used for fertilization.
In cases where semen was collected at surgery or testicular excretory channels before the treatment cycle is generally the cryo sperm to be used.
Whatever its origin, the sperm is analyzed and prepared in the same way. Seminal plasma that limits the power of the fertilizing sperm is eliminated and the most mobile sperm, which are a priori most pollinators are selected.
The oocyte insemination is performed. Depending on the type of infertility, fertilization is left to chance (IVF) or to run (ICSI).
There are two ways to fertilize ova:
1. in vitro fertilization "classic" (IVF) and
2. intra-cytoplasmic injection of sperm (ICSI).
IVF is used as the origin of infertility is female and the sperm quality is normal or slightly altered. A few hours after follicular puncture, the oocytes are reunited with sperm in a culture medium conducive to their survival. They are placed at 37 º C for a period of 4 to 20 hours. Only one spermatozoon - the most active - will cross the zona pellucida and the plasma membrane of the egg and achieve fertilization.
After 18-20 hours of incubation, the biologist look under a microscope if fertilization has occurred. The fertilized ovum (or "impregnated") comes in the form of a cell with two nuclei (pronuclei), one of paternal origin, the other of maternal origin. This stage is called the zygote.
The zygote is not yet an embryo because the genetic heritage maternal and paternal have not yet merged.
At this point, the biologist for the custody transfer 2 or 3 zygotes. The supernumerary zygotes were frozen (cryopreserved) and may be used at a future attempt.
There is sometimes fertilization anomalies that make it impossible to transfer or freezing that these zygotes.
The development and transfer of embryos
Two to three days after the collection of oocytes, embryos are transferred into the uterus. On Day 2, embryos were divided into 2 to 4 cells, the 3rd day, they reached 6 to 8 cells.
The transfer is a painless process. The embryos are placed in a thin flexible catheter. After explaining the cervix with a speculum, the doctor inserts the catheter gently into the uterine cavity. In some cases, the transfer is performed under ultrasound to guide the establishment of the catheter within the uterus and to ensure that the embryos have been tabled in the right place.
Two or three embryos are usually transferred. The number of embryos was decided after discussion with the doctor, depending on the age of the woman and the couple's choice.
Approximately 12 days after the transfer, a pregnancy test performed on a blood test will know the outcome. If the test is positive, an ultrasound will be scheduled approximately 4 weeks after transfer to verify the proper development of the pregnancy.
Cryopreservation of supernumerary zygotes
It is not uncommon that we get more zygotes than the desired number for the transfer. The supernumerary zygotes can be kept at very low temperatures in liquid nitrogen (freezing or cryopreservation).
The aim of cryopreservation of zygotes is to give the couple the best chance to achieve pregnancy, while limiting the occurrence of multiple pregnancy and its complications. The zygote can be thawed and transferred if no pregnancy in the first round. In this case, the stages of the ovarian stimulation and follicle puncture need not be repeated.
The five stages of IVF treatment: (short way of explanation)
1. Hormonal Stimulation of the Ovaries
The woman receives 10 to 14 days, a natural hormone preparations by injection, in order to develop more eggs. In a traditional cycle, one egg is released, but thanks to the hormonal preparation, there are several.
2. Grab or Ovum Pick Up
Puncture or ovum pick up takes place just before ovulation. In this way, the follicles are punctured and sucked so that eggs can be gathered. Around the same time, the man must give a semen sample.
The insemination is to collect the eggs and sperm.
After 16 hours, we can examine whether fertilization took place. Two days later, we can see if the embryos are formed.
5. Transfer of Embryos
Finally, we introduce the (s) best (s) embryo (s) in the uterus.