In today’s article, we will discuss a very important issue for any woman undergoing assisted reproduction treatment: ovarian stimulation or controlled ovarian stimulation (COS). Understanding this step in the context of fertility treatment requires a clear understanding of how a woman’s body works.
How does the ovarian system work?
The ovarian system’s functioning is regulated by the hormonal interaction between the hypothalamus, the pituitary glands (glands located in the brain) and the ovaries. This hormonal axis remains inactive during a woman’s childhood before it becomes active at the time of puberty. It is a kind of communication channel that regulates women’s menstrual cycles, and the language used is hormones. Initially, the hypothalamus secretes the hormone GnRH, which acts on the hypophysis, indicating that it is time for it to secrete two hormones, LH and FSH. These last two are the ones that cause ovulation and stimulate the secretion of reproductive hormones (estrogens and progesterone) by the ovaries.
We must remember that each woman is born with a limited ovarian reserve, i.e. a finite number of cells that will become eggs.
When does it start working?
At puberty, FSH production begins, which induces the growth of ovarian follicles that were ”dormant” or inactive. Under normal conditions, although several follicles are recruited in each menstrual cycle, only one of them will reach ovulation. This dominant follicle will release its oocyte and cause the degradation of the remaining follicles.
The human body is actually a very efficient company. It is not in the nature of the human body to spend more than necessary to accomplish something. That is why it is not normal for women to generate more than one egg per cycle. Thus, those who have twins or twins themselves are truly exceptional. As previously mentioned, ovulation is accompanied by the production of estrogen and progesterone. An elevated blood estrogen level is an indication to the pituitary gland that it has to slow down FSH production because ovulation has already occurred.
Simultaneously, estrogens help the endometrium (the inner layer of the uterus where the embryo implants) to become thicker and thicker. It prepares to receive a possible embryo, resulting from the fertilization of the released egg. Unfortunately, there are many occasions in which the ovarian functioning is not correct or there are obstacles that hinder the encounter between the egg and the sperm. Therefore, in these cases it is convenient to extract the eggs from the woman’s body through surgery (egg retrieval) to fertilize them in the laboratory. This process requires prior ovarian stimulation.
Ovarian Stimulation – What is it?
The objective of ovarian stimulation is to try to make all the follicles ”recruited” in a natural cycle mature instead of degrading. This makes it possible to summarize in a single cycle what a woman produces in a year.
The treatment is carried out with the same hormones that the woman produces herself, but synthetically elaborated.
Ovarian stimulation should begin within the first 3 days of menstruation
This is the time when the ovarian follicles that can potentially produce an egg in that cycle are recruited. If we were to start stimulation later, these follicles begin to degrade and cease to be useful.
We have previously mentioned that FSH levels begin to decrease as estrogen increases in the body. What we do for ovarian stimulation is to take over. Through injections, we continue to provide FSH to the body so that the rest of the follicles (other than the dominant one) continue to mature rather than degrade. There is no selection of a single follicle and this allows us to access a greater number of oocytes in the time of a single cycle. Thus, we have more opportunities to perform in vitro fertilization and obtain more embryos that can lead to pregnancy.
When is ovarian stimulation necessary?
This hormonal treatment is used in most assisted reproduction treatments, whether in vitro fertilisation or artificial insemination. In the case of oocyte donation, the process is also carried out on the egg donor.
But not only is it useful in these cases, but ovarian stimulation is also an essential procedure prior to egg vitrification in fertility preservation treatments.
Ovarian stimulation: from theory to practice.
Normally, before starting stimulation, the doctor will perform a vaginal ultrasound to check that the ovaries are resting.
Ovarian stimulation consists of administering hormonal medication to the woman through subcutaneous injections in order to stimulate the ovaries.
The following are given:
- Gonadotropin hormones. They are administered according to the parameters defined by the doctor for each patient. The evolution of the patients is continuously evaluated in order to adapt the treatment.
- Hcg hormone. This hormone is the final push for the oocytes to finish maturing. It is administered when the follicles are ready to ovulate.
The process will last between 8 and 13 days, until the follicles reach a size greater than 18mm in diameter. Once the HCG is injected, the egg retrieval is scheduled to extract the oocytes.
During the stimulation, the doctor will carry out an ultrasound check every 2 or 3 days and several blood tests. In this way, the doctor will be able to monitor the evolution of the size and number of follicles.
Symptoms and risks of ovarian stimulation
As mentioned above, the hormones administered are completely safe, as they are the same as those produced naturally by the woman.
However, it is true that these hormones are administered in greater quantities than those produced naturally in a menstrual cycle. This results in a number of symptoms that you should be informed about, since they are not a problem.
Since each case is unique, each woman will respond differently to treatment.
Common symptoms include bloating, heaviness, vaginal dryness, stomach upset, and dizziness or nausea. These are temporary symptoms that are usually due to the enlargement of the ovary following treatment.
In any case, you should always consult your doctor, who will adapt the treatment to your condition, in case of an exaggerated reaction or the appearance of severe symptoms.
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