What is the physiological cause of amenorrhea in pregnancy?

Amenorrhea in pregnancy is primarily caused by the hormonal changes that occur after conception. The fertilized egg releases human chorionic gonadotropin (hCG), which signals the corpus luteum to continue producing progesterone and estrogen, hormones that help maintain the uterine lining and prevent menstruation. Additionally, increased levels of these hormones suppress the hypothalamic-pituitary-gonadal axis, inhibiting the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are essential for the menstrual cycle. This hormonal interplay effectively halts menstruation during pregnancy.