In Vitro Fertilization – IVF: What is it?

• It is the union of eggs and sperm in the laboratory.
• This technique overcomes most obstacles to fertilization.
• It is used when there are severe sperm problems, blockage of the fallopian tubes, or other issues that have not been resolved with less complex techniques.
• A woman’s age is the most important factor in predicting success.

When there are complex fertility problems, such as severe endometriosis, blockage of the fallopian tubes, or severely reduced sperm motility, sophisticated assisted reproductive techniques are required. One of these is In Vitro Fertilization.

In Vitro Fertilization involves extracting the eggs from the ovary and bringing them to the laboratory. There, under controlled temperature and humidity conditions, they are exposed to the partner’s sperm to allow fertilization to occur. The fertilized eggs are then incubated for 3 to 5 days until the first cell divisions take place. Once the embryo reaches the multi-cell stage, it is transferred to the uterus through the vaginal route to continue its development.

In Vitro Fertilization overcomes some natural barriers, such as the distance sperm must travel through the woman’s reproductive system before reaching the egg, or the chance that the fallopian tube may fail to capture the egg after ovulation. In fact, IVF controls many variables in the process and is very efficient (>90%) at achieving fertilization and obtaining embryos. However, once the embryo is placed back into the uterus, the implantation process is unpredictable, and the embryo may or may not implant. As a result, IVF offers a pregnancy probability of 45% to 50% per attempt in women under 35 years old.

What is the process like?

The treatment cycle begins with Controlled Ovarian Stimulation: during the first days of the menstrual period, ovulation-inducing medications (gonadotropins – FSH/HMG) are administered to stimulate the development of multiple follicles. This stimulation process lasts approximately eight to nine days (depending on each patient’s response) and is accompanied by ultrasound monitoring, usually performed two or three times, before determining that the follicles are ready and deciding the day for egg retrieval.

At the end of the stimulation phase, a medication (hCG) is added to complete the maturation of the oocytes. Thirty-six hours after administering this medication, egg retrieval is performed. On the day of egg retrieval, the man provides a semen sample to the laboratory to be used for fertilizing the eggs. The egg retrieval is done by inserting a needle into the ovary and aspirating each egg. This procedure is performed under sedation.

The fertilized eggs are allowed to grow in the laboratory for three, four, or five days. After this period, they can be transferred to the woman’s uterus. The transfer is performed with the woman in a gynecological position (similar to a Pap smear), using a thin catheter inserted into the uterus. The procedure is not painful and is done without anesthesia. A few minutes of rest are recommended after the transfer. If there are extra embryos, they can be frozen for transfer at a later time.

During the following two weeks, progesterone (a hormone necessary for the initiation and maintenance of pregnancy) is administered orally, vaginally, or intramuscularly. The pregnancy test is performed 15 days after the procedure.

Are there any risks?

– The main risk is multiple pregnancy. Usually, two embryos are transferred, and either only one implants or both implant, resulting in a multiple pregnancy. Multiple pregnancies carry increased risks for both the mother and the babies.

– Ovarian Hyperstimulation: due to the medications used to stimulate the ovaries, a condition can occur in which the ovaries enlarge and fluid is retained. Severe cases are very rare.

– Pelvic Infection: inserting a needle through the vagina into the ovary could allow microorganisms to ascend from the vagina to the abdominal cavity. This is an extremely rare complication.

What are the chances of success?

A woman’s age is the most important factor in predicting success with In Vitro Fertilization. To explain: while the probability of pregnancy is 50% or higher in women under 35, it is only 27% in women aged 40, and 9% in women aged 42.

What causes this? After birth, a woman does not produce new eggs; on the contrary, they begin to be used up rapidly (around 1,500 per month). The end result is that the older a woman is, the fewer eggs remain in her ovarian reserve. Additionally, as eggs remain in storage, they begin to deteriorate and their fertilization potential decreases.

It is possible to repeat In Vitro Fertilization if the first attempt fails, with cumulative results after three or four attempts exceeding 80%.