What Happens to the Hormones During Pregnancy?

There are many changes in a woman's hormones during pregnancy, but one of the most critical is the production of human chorionic gonadotropin (hCG). Besides a missed period, the presence of this hormone is a primary indication of pregnancy. When doctors perform pregnancy tests or women take in-home pregnancy tests, they are trying to detect this hormone at high enough levels to indicate pregnancy. Progesterone is also important during pregnancy, and increases in the hormone serve to prevent contractions and reduce the production of the hormone prostaglandin. Estrogen levels also rise when a woman is expecting, which helps prepare the body for childbirth, increases uterine blood flow, and stimulates the production of another important hormone called prolactin.

One change that occurs in hormones during pregnancy is the production of hCG in gradually increasing amounts. Once a fertilized egg implants in a woman’s uterus, hCG levels begin to rise gradually. Levels of this hormone in the body usually peak around the 10th or 11th week of pregnancy when the placenta is well formed. Its main role is to ensure the production of the hormones progesterone and estrogen until the placenta is fully formed and takes over.

When discussing changes in hormones during pregnancy, progesterone is usually mentioned as well. During a pregnancy, progesterone levels rise gradually. This hormone, which is primarily produced by the placenta, works to prevent contraction of the uterus and reduce prostaglandin production. Prostaglandin is a substance that is produced by the bodies of both men and women. It stimulates contractions and is sometimes administered to pregnant women for the purpose of preparing the cervix for childbirth.

Estrogen is also among the hormones that rise during pregnancy. Mainly produced by the placenta, estrogen has important roles to play in increasing blood flow in the uterus and stimulating the production of the hormone prolactin. Increases in prolactin during pregnancy serve to prepare the body for lactation after childbirth.

Changes in hormones during pregnancy may be a primary factor in the emotional upheavals that are common to pregnant women. For example, it is common for a pregnant woman to have periods of feeling happy that give way to crying and sadness for reasons that are difficult to fathom. Sometimes crying occurs during pregnancy not because of sadness but due to a woman’s joy at being pregnant. While this may also occur as a result of true happiness, changes in hormones are an influence.