What causes menstrual cycles to stop during pregnancy?

During pregnancy, the menstrual cycle ceases primarily due to hormonal changes that support the pregnancy. The continued presence of estrogen is crucial because it plays a significant role in maintaining the endometrial lining of the uterus. When a woman becomes pregnant, the placenta starts to produce hormones, including estrogen and progesterone, which help sustain the pregnancy and inhibit the typical hormonal fluctuations associated with the menstrual cycle.

The elevated levels of estrogen, along with progesterone, work together to prevent ovulation and the shedding of the uterine lining, which are key components of the menstrual cycle. Without these hormonal changes, the normal cycle would continue, leading to menstruation. However, during pregnancy, the body prioritizes the maintenance of the developing fetus, and thus the menstrual cycle stops.

Other options do not accurately describe the main hormonal changes that lead to the cessation of the menstrual cycle during pregnancy. For example, while luteinizing hormone plays a role in ovulation, its levels reduce during pregnancy rather than being the direct cause of menstrual cycle cessation. Similarly, low levels of progesterone would not sustain a pregnancy; in fact, progesterone levels must be sufficiently high to maintain the uterine lining. Increased testosterone levels are not typically associated with normal female physiology during pregnancy and do