The Role of Hormones during Pregnancy

The Role of Hormones during Pregnancy

A woman's first pregnancy is one of the most exciting and dramatic events of her life. As conception progresses to implantation, and an embryo eventually becomes the fetus that ultimately will be the highly anticipated bundle of joy, numerous changes take place within the woman's body to enable this miraculous process to occur. While a woman's physical changes may be obvious, several other ones may be subtle, including a growing sense of immense emotional attachment and reprioritization. The vast majority of these changes are attributable to the hormones of pregnancy.

The first trimester of pregnancy begins with conception. As egg and sperm unite, and the conceptus implants into the endometrium or uterine lining, a hormone called human chorionic gonadotropin (HCG) is produced. HCG has a very predictable rise in the early weeks of pregnancy and peaks around 70 days. HCG is thought to support the pregnancy by ensuring ovarian production of progesterone until the placenta is well formed around the tenth week. HCG is thought to be the hormone responsible for a number of symptoms associated with early pregnancy, namely nausea and resultant vomiting and the sometimes overwhelming fatigue that can plague the very early expectant woman.

Progesterone is one of the major hormones of pregnancy and is primarily produced by the placenta. Levels of progesterone in the body rise as pregnancy progresses. Progesterone functions to inhibit the smooth muscle in the uterus from contracting and decreases prostaglandin formation, both of which allow the fetus to grow with the expanding uterus. As progesterone levels increase, other smooth muscle in the body may also be affected, such as that in the lower esophageal sphincter, which results in increased heartburn and acid reflux, especially in the later stages of pregnancy. Progesterone softens cartilage as well and may be responsible for the commonly occurring hip and pubic bone pain that also occurs. This hormone also can cause tenderness in the breasts early on and the bloated feeling many women experience throughout pregnancy.

Estrogens also increase during pregnancy and are also produced primarily by the placenta. Among other functions, estrogens increase uterine blood flow. Prolactin, the hormone that allows for lactation postpartum, also increases throughout pregnancy, and its production is thought to be stimulated by increasing levels of estrogens.

The rise in estrogen, as well as progesterone and other hormones in pregnancy, is also in part responsible for the magnification of emotions a pregnant woman experiences. Increased circulating levels intensify the myriad of feelings a pregnant woman has. The joy of being pregnant may often move a woman to tears. Anxiety in regard to how a woman may feel about herself and the way her body is changing is normal, and her concerns regarding her own health and the health of the fetus are paramount. Anticipation of the new role of being a mother and the changes a new baby will bring to the family may be overwhelming. The pregnant woman should be encouraged and supported by her spouse, family, and health care providers in all her concerns.

After delivery, hormone levels rapidly decrease, and their fall may contribute to postpartum adjustment issues and postpartum depression. During this time, it is very important that the new mother be aware that being overwhelmed is normal to some extent, but if these feelings are pervasive, she should seek medical attention. Occasionally, very low dose hormone replacement may be of help, as can antidepressants.

A newborn in its mother's arms is the result of an incredible orchestration of numerous events, many of which are primarily the result of the vital role hormones play in pregnancy. Talk to your health care provider about any questions or concerns you may have regarding the role of hormones in pregnancy, and he or she will be happy to elaborate.

Editorial provided by Anandi Subramanian, MD. Dr. Subramanian is a practicing OB-GYN in Norwalk, CT. She is with Women's Health Care of New England and has offices in Norwalk, New Canaan, and Ridgefield, CT.