- Estrogen: In pregnancy, estrogen stimulates the growth of the uterus and improves blood flow between the uterus and placenta. It also preps the breasts to prepare for milk production by enlarging a woman's milk ducts. Peak estrogen secretion happens right before birth.
- Progesterone: This hormone helps maintain the inner layer of the uterus to provide support for the developing embryo. It also serves the very important role of quieting the uterine muscle, so the blastocyst can have a safe landing while implanting.
- Human Placental Lactogen: Besides helping with milk preparation, this hormone also increases a mom's metabolism during pregnancy (she needs more energy caring for another human, after all).
- Human Chorionic Gonadotropin: This hormone stimulates the corpus luteum (the part of the follicle left behind in the ovary) to produce estrogen and progesterone in the first 10 weeks after conception, until the placental cells can do so by themselves. (For this reason, it is also the hormone we check in your urine or blood to determine whether you're pregnant.) Levels of hCG, which have been associated with morning sickness, typically peak toward the end of the first trimester, then decline and level off for the rest of the pregnancy.
Find out more about this book:YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy