Hormones During Pregnancy: What You Need to Know

Oxytocin, human chorionic gonadotropin, and estrogens are some examples of vital hormones during pregnancy. We'll you about the most important ones.
Hormones During Pregnancy: What You Need to Know

Last update: 01 July, 2021

The presence of hormones during pregnancy is very important for the proper development of the future baby. Many of these substances are released cyclically during the menstrual period, but during pregnancy, they play a different role.

Are you interested in knowing a little more about this topic? In the following paragraphs, we’ll mention the five most important hormones, their main functions, and some other interesting facts. This won’t only give you a better understanding of your body, but will also highlight once again the great complexity of pregnancy. Keep reading!

What are hormones and what are they for?

Hormones are very important substances for the proper functioning of the whole body. Their composition varies, although in most cases, they’re made up of proteins or small amounts of amino acids.

They’re released in organs called endocrine glands. Hormones must travel through a large part of the body – usually via the bloodstream – to reach other organs and cause changes in their functioning.

This is how, for example, the pituitary gland releases oxytocin. This gland is at the base of the brain and reaches the muscle of the uterus to cause the contractions that are so characteristic during labor. Interesting, isn’t it?

Some important hormones during pregnancy

All physiological changes in a woman’s body to achieve the development of the future baby in her uterus are a consequence of hormonal changes. Some of these hormones aren’t present in the male body, which makes this process much more special and characteristic.

Below, we’ll tell you about the substances that are most involved during gestation and their importance.

1. Human chorionic gonadotropin or HCG

A woman looking at a home pregnancy test.
This is the substance that pregnancy tests mesaure.

Human chorionic gonadotropin or HCG is one of the first hormones to appear during pregnancy. The baby itself produces it (although at this stage, we refer to the baby as an embryo) to allow the development of the surrounding structures that’ll allow it to grow in the uterus.

Pregnancy tests using a blood or urine sample detect elevations of this substance, which makes it possible to “diagnose” early pregnancy. When levels are abnormally high, gestational trophoblastic disease is likely, which can lead to complicated cases of cancer during pregnancy.

2. Progesterone, one of the important hormones during pregnancy

Progesterone is one of the hormones during pregnancy that also appears at other times in a woman’s life. In fact, it’s important in the menstrual cycle and, when its concentrations fall, the endometrium detachment occurs, which produces menstrual flow.

Several organs are responsible for its production, notably the ovaries (female reproductive organs in women) and the placenta. During pregnancy, it fulfills several functions, including inhibiting the mother’s immune system to preventing rejection of the embryo or fetus.

In fact, multiple investigations have revealed the role that progesterone injection can play in preventing miscarriage in mothers with risk factors.

3. Estrogens

Estrogens are the female sex hormones par excellence, something similar to what happens with testosterone in men. Outside pregnancy, they have multiple functions, since they influence the processing of some nutrients and the development of secondary sexual characteristics.

They’re also produced by the placenta and are in charge of favoring the development and adaptation of the uterus and vagina for the growth of the baby and childbirth, respectively. Just as what happens during the menstrual cycle, estrogens are likely to contribute to mood changes at this stage.

Find out more: How a Baby is Conceived

4. Oxytocin, another of the most important hormones during pregnancy

A pregnant woman connected to a fetal monitor.
This hormone promotes uterine contractions.

Oxytocin is one of the most well-known hormones during pregnancy – you’ve probably heard of it! The pituitary gland -or neurohypophysis, to be more specific – is responsible for its synthesis, and this hormone’s responsible for stimulating uterine muscle contractions when it’s time for labor.

As discussed in this scientific review study (2020), oxytocin injection is a common practice to facilitate labor in hospital settings. Although there may be complications from its use, such as uterine rupture, experts generally consider it to be a safe substance.

5. Prolactin

Like the previous one, prolactin is quite well known and its name helps us somewhat to understand its function. It also originates in the pituitary gland, although in its anterior portion, or adenohypophysis. Its elevated concentrations are related to the stimulation of the mammary glands to facilitate the production of breast milk.

This happens in the moments prior to delivery, with the aim of providing sufficient nutrients to babies as soon as they’re born. Although its production can take place during the rest of the pregnancy in significant quantities, high levels of progesterone and estrogen “block” the release of breast milk.

The mother’s body is a very complex system

If you didn’t already know, it’s clear from reading this article that pregnancy’s a very complex event! In general terms, this is what we know about the main hormones during pregnancy, but there are still many questions to be answered, especially in regard to conception.

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  • Velásquez N. La hormona gonadotrofina coriónica humana. Una molécula ubícua y versátil. Parte I. Rev Obstet Ginecol Venez 2014;74(2):122-133.