In vitro fertilization (IVF) is a technique whereby fertilization is carried out outside the mother's body. IVF is the main treatment for infertility when other assisted reproductive methods have not succeeded. The process involves hormonal control of the ovulatory process, through hormonal stimulation that makes it possible to obtain multiple oocytes for IVF in most cases. Oocytes are retrieved from the maternal ovaries by follicular puncture, guided by vaginal ultrasound. The fertilized oocyte (zygote) is kept in culture for several days (2-5 after ovarian puncture) before the resulting embryo is transferred to the woman's uterus, in order to allow its implantation and subsequent development until childbirth.
Blockage or absence of the fallopian tubes.
Problems at the level of the uterine cervix.
Failure of artificial insemination.
Sterility of unknown origin.
Low quality of spermatozoa.
Low quality of oocytes.
In classic (or conventional) IVF, spermatozoa and oocytes are obtained by masturbation and ovarian puncture, respectively.
The retrieved oocytes are placed in a suitable culture medium and incubated at 37ºC and under a gas phase of 90% N2, 5% O2 and 5% CO2. Next, the semen sample is requested from the patient. Spermatozoa are washed from the seminal plasma and capacitated in vitro, to be subsequently used for in vitro insemination. Insemination is carried out by mixing the oocytes with an adequate concentration of capacitated spermatozoa in suspension.
Currently, most IVF attempts are made by microinjecting spermatozoa directly into the cytoplasm of the ovules using the technique of intracytoplasmic sperm injection (ICSI). The methods of ovarian stimulation, oocyte collection and sperm preparation are the same as for classic IVF. Unlike classic IVF, however, a single selected spermatozoon is microinjected into each of the available oocytes, after removing the cumulus oophorus cells from its surface. The cumulus removal makes it possible to determine if the oocyte is mature or immature, and in the latter case, the oocytes are kept in the culture medium until they complete maturation before being injected. The results of ICSI are superior to those of classic IVF in all cases of problems with sperm movement and ability to react with the oocyte.
Signs of fertilization are looked for on the day after oocyte retrieval, and the patients receive the information on the number and quality of fertilized oocytes (zygotes) at that time. These data are merely preliminary, since all zygotes usually do not form a normal embryo by the day the uterine transfer of the embryos to the uterus is scheduled (1-4 days later). The embryos are selected according to their morphology and the number of cells (blastomeres) resulting from the successive divisions of the zygote. Embryos with serious morphological abnormalities and those that have stopped their cell division are not transferred.
Therefore, 1-5 days after the follicular puncture, one to three resulting embryos (the best quality ones) are transferred to the patient's uterus. This number of embryos has been shown to provide the highest chances of pregnancy, with the lowest risk of giving rise to a multiple pregnancy.
In any case, the number of embryos to be transferred will be agreed with the couple depending on their wishes and possibilities. The transfer procedure lasts only a few minutes and is carried out under ultrasound control with the use of a fine catheter. The patient will then rest for a couple of hours after which she can get back home. The procedure is, like artificial insemination, simple and completely painless.
Once at home, the patient will take a rest and observe sexual abstinence for 7 days (advisable). She will follow the treatment given by the doctor, which is normally based on progesterone to improve hormonal values during the luteal phase and facilitate the chances of implantation and subsequent pregnancy.
About 14 days after the transfer, a blood pregnancy test (beta-HCG measurement) will be carried out. The result will be communicated to the clinic. If the result is positive, an ultrasound will be performed 2 or 4 weeks later. Once the presence of an embryo sac with heartbeat is confirmed, the doctor will inform the patient about further steps to follow during pregnancy.
Good quality embryos that are not transferred are frozen (vitrified) in order to increase the couple's chances of becoming parents again (if the first IVF attempt was positive) or to try again (if the attempt failed).
In any case, the frozen embryos will belong to the couple for a period of 5 years. Thereafter, if the couple does not express interest in them, they will become the property of the assisted reproduction clinic and may be used in an embryo donation program, depending on an informed consent by the biological parents.