Normally during the course of the menstrual cycle a single egg is released from the ovary. This one egg is selected out of over 1000 potential eggs. This one egg inside its follicle is selected because it happens to be at the right point in its development. It has the most receptors for the hormone FSH (follicle stimulating hormone). As this follicle starts to develop the cells around the egg release estrogen. This estrogen can lower the amount of FSH in the body so other follicles do not develop. This is the body’s natural way of preventing a multiple pregnancy.
Ovulation induction or ovarian stimulation can increase the number of eggs released in a cycle. There are medications that can be taken orally to help the pituitary release additional FSH to potentially allow for more than one follicle to develop. FSH can also be given directly as an injection, this is a more powerful way of producing more follicles which means more eggs.
Increased numbers of eggs being released can increase the chance that one of these eggs will be fertilized and make it to the uterus for implantation. If 2, 3 or 4 eggs are released in that month it can be equated to 2, 3 or 4 months of trying to get pregnant put into one month.
The ovulation induction is a great treatment to try for several cycles. If not successful after 3-4 treatments, it would be better to consider a treatment like in vitro fertilization (IVF).
Ovulation induction requires functioning fallopian tubes and good sperm. If either the sperm quality or the tubal function is compromised the treatment does not have a significant chance of causing a pregnancy. IVF is a better option for these patients.
Process of Ovulation Induction
Ovulation induction or ovarian stimulation can be done with medications taken orally or by using medications that are given as a subcutaneous injection. Sometimes a combination of these two types of medications are used. The goal is to get from 2-6 follicles to develop, sometimes more if the woman is older than 40.
During the ovarian stimulation, ultrasound examinations may be used along with estrogen determinations to follow the development of the follicles. When the follicles have developed to the appropriate size, they are prepared for release, and a trigger medication is used to allow for the final maturation of the egg inside the follicle. In this final maturation step the egg gently lifts off the side of the follicle wall and floats in the middle of the follicular fluid on a small tether of cells.
As the egg(s) release the patient is instructed on when to have intercourse or if an intrauterine insemination (IUI) is being done, it will be timed for the ovulation.
This ultrasound image shows fully stimulated ovaries. Each of the grape-like follicles (15 to 25 mm in diameter) contains a microscopic egg.