How do estrogen and progesterone prevent further ovulation during pregnancy?

During pregnancy, the body prevents further ovulation through a process of negative feedback involving the pituitary gland and the hypothalamus.1

High levels of estrogen and progesterone—secreted initially by the corpus luteum and later by the placenta—act upon the pituitary gland to suppress the secretion of gonadotropic hormones, specifically follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Under normal conditions, FSH and LH are required to stimulate the growth of ovarian follicles and trigger the release of a mature egg. By inhibiting the release of these gonadotropins, the elevated levels of estrogen and progesterone effectively prevent the development and release of additional eggs, thereby ensuring that the pregnancy remains undisturbed. This same biological mechanism serves as the basis for the design of oral contraceptives.123