Maternal physiological changes in pregnancy range of effects during the pregnancy. Pregnant women experience numerous adjustments in their endocrine system that help support the developing fetus. The fetal-placental unit secretes steroid hormones and proteins that alter the function of various maternal endocrine glands. Sometimes, the changes in certain hormone levels and their effects on their target organs can lead to gestational diabetes and gestational hypertension. Levels of progesterone and estrogen rise continually throughout pregnancy, suppressing the hypothalamic axis and subsequently the menstrual cycle. The progesterone is first produced by the corpus luteum and then by the placenta in the second trimester. Women also experience increased
Breast development lactation by prolactin. Expression of the PRLR in breast tissue may increase by as much as 20-fold when estrogen and progesterone levels drop upon childbirth. With suckling from the infant, prolactin and oxytocin are secreted and mediate milk production and letdown, respectively. Prolactin suppresses the secretion of LH and FSH, which in turn results in continued low levels of estrogen and progesterone, and temporary amenorrhea (absence of menstrual cycles) occurs. In the absence of regular, episodic suckling, which keeps prolactin concentrations high, levels of prolactin will quickly drop, the menstrual cycle will resume and hence normal estrogen and progesterone levels