Female reproductive system. Pregnancy and childbirth. Lactation.
Pregnancy is the period of fetal development within the mother's uterus, typically lasting about 40 weeks in humans. It is a complex physiological process involving significant hormonal changes and adaptations in the mother's body to support the growing fetus.
Hormonal Changes During Pregnancy
- Estrogen and Progesterone: Levels of these hormones, initially produced by the corpus luteum and later by the placenta, rise steadily throughout pregnancy. They play crucial roles in:
- Maintaining the endometrium to support the developing embryo and fetus.
- Preparing the breasts for lactation.
- Suppressing the development of new ovarian follicles.
- Human Chorionic Gonadotropin (HCG): This hormone, produced by the trophoblast (which develops into the placenta), signals the corpus luteum that fertilization has occurred. HCG maintains the corpus luteum's production of estrogen and progesterone during early pregnancy. HCG levels peak around the 9th week of gestation and then decline.
- Human Placental Lactogen (hPL): Produced by the placenta, hPL has actions similar to growth hormone and prolactin. It helps regulate maternal metabolism and nutrient availability for the fetus.
- Prolactin: Levels of prolactin, the hormone responsible for milk production, increase gradually throughout pregnancy. However, lactation is inhibited by high levels of estrogen and progesterone.