When a woman is going to undergo fertility treatment, she should use medication to stimulate the ovaries. This is called controlled ovarian stimulation (SOC). Medicines used to stimulate the ovaries contain hormones that naturally affect the menstrual cycle, and their role is to create more than one egg. Depending on the fertility treatment and the number of eggs required, one or two eggs for artificial insemination (AI) and several during in vitro fertilization (IVF pregnancy), the stimulation will be more or less light. It is controlled by hormonal dosage and ultrasound control. Use of hormonal drugs At the beginning of each menstrual cycle, a group of eggs matures in the ovary inside small fluid-filled sacs: follicles. This group is called follicles. The hormonal flow between the hypothalamus, pituitary gland and ovaries means that only one of these follicles will fully develop into a pre-ovulatory follicle. This leads to the degeneration of the rest of the follicles and the loss of the eggs in them. The hormones FSH and LH, secreted by the pituitary gland, regulate all follicular development and allow the follicle to ovulate by the middle of the menstrual cycle. In the PMA area, the patient must follow a specific hormonal treatment during the menstrual cycle because several mature follicles are required if one wants to increase the chances of pregnancy. These drugs aim to trick the ovaries into allowing the entire follicular group to mature. Therefore, ovarian follicles that were supposed to be destroyed continue to grow and produce mature eggs that can be fertilized. Types of hormonal drugs Several medications can be used in controlled ovarian stimulation, but they generally fall into one of two groups: ### GnRH analogs and gonadotropins. These two types of drugs have different functions and are necessary for any artificial insemination or in vitro fertilization treatment. There are still exceptions, such as IVF in a natural cycle. ### Endometrial preparations Although it is not part of ovarian stimulation, women on MPA cycles must take medication to prepare their endometrium. The drugs used for this purpose mainly consist of sex hormones that are naturally secreted by the ovaries (estrogen and progesterone) and should be taken immediately after the follicle is punctured. The following drugs are prescribed to prepare the endometrium: - Medicines containing estrogen - Medicines containing progesterone The thickness of the endometrium plays a very important role in embryo implantation. Therefore, good preparation of the endometrium is necessary to achieve pregnancy. **There are several strategies to improve endometrial or uterine receptivity in patients with poor receptivity.** Ovarian stimulation process Currently, there are two protocols or methods for administering hormonal drugs during SOC: the long process and the short process. The main difference between the two is the duration and number of injections to be performed. The doctor responsible for the treatment must decide which of the two protocols to follow and adapt the dosage of the medicine necessary for each woman always to her characteristics and with the aim of achieving the best possible success. ### Long protocol By administering GnRH agonist in the previous menstrual cycle, it starts on the 21st day of the cycle. About 10 to 14 days later, the woman gets her period. At this stage, stimulation of the ovaries by gonadotropins can begin. Between the first and third day of your period, your doctor will tell you the daily hormonal dose of FSH that you should take. Once the ultrasound confirms that the ovarian follicles have reached the appropriate size (between 18 and 20 mm) and the estradiol level is optimal, the doctor tells the woman that she needs to inject hCG to induce final maturation. Follicular puncture should be performed before 36 hours to prevent spontaneous ovulation. ### Short process In this case, ovarian stimulation begins with the administration of gonadotropins at the beginning of the menstrual cycle, between the first and third day after the onset of menstruation. Normally, to synchronize the patient's cycle, contraceptive pills are prescribed in the previous cycle. After about 5 days of follicle stimulation and growth, a GnRH antagonist medication is administered to prevent the endogenous LH surge that triggers ovulation.