Ovarian cysts usually originate from an ovarian follicle that didn’t ovulate, thereby called a follicular cyst. Sometimes ovarian cysts can originate from the yellow body (corpus luteum) that should normally transform into a white body (corpus albicans) and disappear at the end of the cycle. These are called luteal cysts.
Birth control pills contain synthetic estrogen and progesterone that suppress the hypothalamus to secrete Gonadotropin realizing hormone (GnRH) and stimulate the pituitary gland to secrete Follicular stimulating hormone (FSH) and Luteinisating hormone (LH). FSH is responsible for follicle maturation and LH for ovulation. When a follicle becomes mature enough, LH causes a rupture of the mature follicle and expells the egg-cell (ovulation). After ovulation ,the rest of the follicle turns into a yellow body. When using birth control pills, maturation and ovulation of the follicles stops because there is no FSH and LH introduced to the system. Sometimes a follicle may reach a level of maturation (but not enough to ovulate) because there is not enough FSH and LH. Such an example of an immature follicle may turn into a follicular cyst. Follicular cysts usually produce estrogen that temporarily disturb the menstrual cycle (delayed period).