Pregnancy hormones 101: Your guide to what’s going on inside your body

Whether you are pregnant, considering surrogacy, or supporting someone who is pregnant, you understand the impact that fluctuating hormones can have on daily life. These hormonal changes can cause nausea, mood swings, and significant alterations to the body as it adapts to accommodate a growing baby. Have you ever wondered about the science behind these changes?

Below, we will briefly explore some of the key hormonal fluctuations that occur during pregnancy and the reasons behind them to help you gain a better understanding of the process.

During pregnancy, the body undergoes unique hormonal and physiological changes. One of the first major hormonal fluctuations is in human chorionic gonadotropin (hCG). Produced exclusively during pregnancy, hCG plays a crucial role and is primarily produced in the placenta. It is the hormone measured in urine tests to confirm early pregnancy, with levels increasing exponentially each day and peaking in the first trimester.

The role of hCG is to stimulate the production of elevated levels of estrogen and progesterone to maintain the pregnancy. As the placenta matures and begins producing progesterone and estrogen independently, hCG production decreases. Before this occurs, the ovaries produce these two principal pregnancy hormones, which support fetal development, facilitate the transfer of nutrients, and perform other essential functions.

Estrogen, for example, is crucial for the development of female sexual traits and enhances vascularization—the formation of blood vessels. This hormone also plays a significant role in the development of milk ducts, leading to the enlargement of breasts during the second trimester. Estrogen levels steadily increase, reaching an extraordinarily high peak in the third trimester.

During pregnancy, progesterone levels are also significantly elevated. This increase causes a loosening of ligaments and joints throughout the body, facilitating the movement of organs as the uterus expands to accommodate the growing baby. Additionally, progesterone helps the uterus grow from the size of a small pear in its non-pregnant state to one capable of carrying a full-term baby in a relatively short time.

After delivery, estrogen and progesterone levels decrease dramatically as the body returns to a non-pregnant state. This rapid decline can result in a temporary hormonal imbalance and lead to various emotional reactions, such as the “baby blues.” Managing these hormonal fluctuations can be challenging, but expectant mothers and surrogates, as well as those utilizing surrogacy parenting services, are encouraged to seek support, prioritise sleep, and engage in moderate exercise to regulate stress hormone production and increase endorphins.

These are just three of the hormones that fluctuate significantly during pregnancy. If you would like to learn more, please refer to the accompanying resource from the International Surrogacy Center.