Oral contraceptive pills (OCPs) are the most commonly used method to prevent pregnancy. So, why are they often used at the beginning of 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.

OCPs are typically made of two hormones, estrogen and progestin. When OCPs 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 OCPs 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. Egg donors are often put on OCPs to coordinate their follicles with the intended mother or gestational carrier for a successful fresh transfer.

OCPs 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 OCPs can help reduce the stress and unpredictability of this process.