Understanding In Vitro Fertilization (IVF)

Once the basics are understood, it’s important to know that women are born with a limited reserve of all the eggs they will ovulate throughout their lives, each of them within its own follicle. At the beginning of each cycle, the ovary selects a few candidate follicles from this imaginary pool, known as the “follicular cohort.” These candidates can be observed in the gynecological ultrasound, this is called the antral follicle count, and we perform it before any treatment. The follicles that have been selected, are directly related to the ovarian reserve. The more follicles in the follicular cohort, the greater the ovarian reserve is. Under natural conditions, out of these selected candidates, only one, the most sensitive or dominant one, will grow and ovulate around day 14 of the cycle. At the end of the cycle, all those candidates that haven’t become the dominant follicle are lost, and the ovary selects a new cohort of follicles to start all over again in the next cycle.

To undergo IVF, ovarian stimulation treatment is necessary. Ovarian stimulation involves artificially administering the same hormones that the brain naturally secretes but in larger quantities. Why? Well, to ensure that all the candidates from that month’s cohort develop simultaneously and give rise to several mature eggs, not just one. This treatment is administered through small injections in the abdomen starting from the first day of menstruation, and we monitor everything through ultrasound in the clinic.

When we observe that several follicles have reached an adequate size (which is related to the maturity of the eggs they contain), we schedule the egg retrieval or ovarian puncture, usually around day 14 of the cycle.

Ovarian puncture is a brief 10-15 minute surgery in which, while the woman is asleep, we access the ovaries using a vaginal ultrasound probe, similar to the ones gynecologists use in regular consultations. This probe has an incredibly fine needle through which we can access the ovaries, puncture them, and aspirate the contents of the multiple developed follicles. This way, we can “catch” the eggs and take them to the laboratory, which is usually adjacent to the operating room.

This is when the embryologists come into play: on the same day of the puncture, if a man is involved, he will need to provide a sperm sample. If it’s a frozen donor sample, it is thawed. The embryologists ensure fertilization takes place and place the fertilized eggs (embryos) in an incubator where they stay for 3 to 5 days (always recommended for 5 rather than three). Once prepared, they can be implanted in the woman’s uterus through what is known as embryo transfer.

The transfer of embryos to the uterus is carried out through a simple procedure without anesthesia, in which a fine catheter is inserted through the cervix to deposit the embryo inside the uterus. The advice is to transfer embryos one by one, especially if they are 5-day-old embryos. This helps minimize the risk of multiple pregnancies, which is always risky for both babies and mothers.

Between 9-14 days after the transfer, a blood or urine pregnancy test can be done to see if the embryo has successfully implanted in the uterus and monitor its development.

It’s important to emphasize that success cannot be guaranteed in all cases. You see, in practice, not all ovarian follicles we see on ultrasound contain eggs, not all eggs we retrieve are suitable for use, and not all sperm manage to fertilize the egg. Similarly, not all embryos survive the 5-day embryonic culture, and not all of them will be able to implant in the uterus. Therefore, unfortunately, we are far from having a 100% success rate.

To give you a realistic idea, for each 5-day embryo transfer, there is around 30- 50% pregnancy rate, so sometimes perseverance and patience are necessary. It’s like an obstacle course that needs to be overcome step by step. The important thing to keep in mind is that the more eggs there are initially, the better the chances of reaching the end of the journey. In any case, due to all the implications of the treatment, it is a psychological challenge for everyone. That’s why it’s crucial to be well emotionally supported by friends, healthcare professionals, and family from the beginning to the end, to handle uncertainty and possible emotional ups and downs in the best possible way.