Birth control pills (BCPs), or oral contraceptive pills (OCPs), are the most commonly used method to prevent pregnancy. So, why are birth control pills often used at the beginning of IVF fertility treatment?
At the beginning of the menstrual cycle, each ovary has several small “follicles”, or sacs. Each follicle has an immature egg inside, just waiting to grow and mature. The pituitary gland in the brain sends a hormone called follicle stimulating hormone (FSH) to the ovaries, telling them to grow a follicle. When the one (or sometimes two) follicle(s) grow, they send a signal, estrogen, back to the pituitary gland to let it know, “Hey, I’m growing up!” This tells the pituitary gland to stop sending out FSH, which stops telling the ovaries to make follicles.
Birth control pills are typically made of two hormones, estrogen and progestin. When BCP's are taken near the beginning of the menstrual cycle, the extra estrogen tricks the pituitary gland into thinking a follicle is already growing, so it does not send out FSH to grow follicles. This will effectively put the woman’s cycle on hold. Once OCPs are stopped, the estrogen levels will decrease again and the pituitary gland will resume sending out FSH.
It is very common for women to take birth control pills with fertility treatment in order to time their menstrual cycle. By putting their cycle on hold, they can plan their work schedules, or vacations with their IVF medication schedules. Birth control pills for IVF do not always have to be used, and in this case the intended mother would simply wait for a period to begin treatment. As most women know, periods are not always predictable. This can make the fertility treatment process more stressful. The use of birth control pills can help reduce the stress and unpredictability of this process.
Egg donors are often put on birth control pills to coordinate their follicles with the intended mother or gestational carrier for a successful fresh transfer.
Once an egg donor is matched with an egg recipient(s), the egg donation process itself can begin! Traditionally, the next step is to sync the menstrual cycles of the egg donor and egg recipient. Menstrual cycle syncing is most commonly done using birth control pills. This allows fresh embryos to be transferred to the recipient, a few days after the eggs are collected and fertilized. However, it is becoming more common to freeze either the eggs or the embryos and transfer them in a future cycle. Syncing menstrual cycles is not needed if the eggs or embryos are frozen.