What physiological process is responsible for the cessation of ovulation during pregnancy?

Ovulation ceases during pregnancy primarily due to the high circulating levels of estrogen and progesterone. When a woman becomes pregnant, the developing placenta begins to produce these hormones, which play a crucial role in maintaining the pregnancy and creating an environment conducive to fetal development. The elevated levels of estrogen and progesterone inhibit the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn leads to reduced secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. Since LH and FSH are critical for the maturation and release of ovarian follicles, their decreased levels prevent ovulation from occurring.

This hormonal feedback mechanism is essential to ensure that the body focuses on nurturing the developing fetus rather than preparing for another potential ovulation and pregnancy. Thus, high levels of estrogen and progesterone directly maintain the quiescent state of the ovaries during pregnancy, effectively preventing ovulation.