During pregnancy, many hormone levels change in the body, with several hormones playing major roles. The most important pregnancy hormone is human chorionic gonadotropin (hCG), which is only produced during pregnancy and is made almost exclusively in the placenta. HCG hormone levels found in maternal blood and urine increase dramatically during the first trimester and may contribute to nausea and vomiting that are often associated with pregnancy. Other important hormones during pregnancy include:
-
Human placental lactogen (hPL): This hormone, produced by the placenta, helps provide nutrition to the fetus and plays a role in stimulating milk glands in the breasts in anticipation of breastfeeding.
-
Estrogen: This group of hormones is responsible for developing the female sexual characteristics. Normally formed in the ovaries, estrogen is also produced by the placenta during pregnancy to help maintain a healthy pregnancy.
-
Progesterone: This hormone is produced by the ovaries and by the placenta during pregnancy. Progesterone stimulates the thickening of the uterine lining in anticipation of implantation of a fertilized egg.
Other hormones that play a role during pregnancy include oxytocin, prolactin, and relaxin.
