Relationship between hCG, estrogen, and progesterone

•Also causes the corpus luteum to double in size during the first two months of pregnancy

•Stimulates the corpus luteum to secrete large amounts of estrogen and progesterone

•Estrogen and progesterone are necessary for the continued growth of the endometruim

•If the corpus luteum is removed during the first 7 to 10 weeks of pregnancy, spontaneous abortion will occur

•During the second month of pregnancy the placenta is able to secrete estrogen and progesterone on its own

Placental Secretion of

Progesterone

•By week 12 (3 mo fetal development) the placenta extracts cholesterol from the maternal circulation

•Uses cholesterol to make progesterone

•Essential for maintenance of pregnancy

•Stimulates secretion of nutrients from glands in the endometrium for nurishment

•Inhibits contractions in the uterus

Placental secretion of Estrogen

•After the first two months of pregnancy the placenta secretes estrogen

•Circulating levels of estrogen continue to rise usually 100X higher than the highest concentration during the ovarian cycle

•Estrogen from the placenta stimulates enlargement of the uterus and breasts

Human Chorionic

Somatomammotropin

•The placenta secretes hCS at about 4 weeks of pregnancy

•Levels rise steadily during pregnancy

•Structure is similar to human growth hormone

•hCS has anti-insulin actions – decreases maternal utilization of glucose

•Makes more glucose available to the fetus

•Also promotes release of free fatty acids from fat stores