Fertility medications are used in the introductory stage of treatment. They are designed to stimulate the ovaries to produce multiple mature eggs (oocytes) rather than the single egg that normally matures during a natural cycle. Retrieval of multiple eggs increases the probability of pregnancy since it means several embryos may be available for placement in the uterus.
The medications used to maximize egg production include:
- GnRH Analogues — Used to suppress the natural production of follicle stimulating hormone (FSH) and luteinizing hormone (LH) hormones in order to control the menstrual cycle and improve the quantity of eggs retrieved.
- Gonadotropins (FSH) — Synthetic forms of pituitary hormones used to stimulate the growth of follicles in the ovaries, which nourish the eggs. Follicle growth is needed during stimulation to produce healthy eggs.
- Human Chorionic Gonadotropin (hCG) — Used at the end of a stimulation cycle to induce final maturation of the eggs. While these drugs sometimes are used to induce ovulation, when given in this process, the egg retrieval is timed to allow the eggs to be collected before ovulation occurs.
During the use of gonadotropins, the concentration of estrogen and progesterone circulating in the blood reach levels higher than normal. In a typical stimulation cycle, approximately five blood tests will be collected during the course of medication to monitor these levels. The follicle growth will also be monitored by vaginal ultrasound. Once the appropriate follicle size is achieved, FSH is discontinued and a single dose of hCG is given for final maturation of the eggs. The egg retrieval typically occurs 35-36 hours later.