What happens to your hormones during pregnancy?

What happens to your hormones during pregnancy?


Even though I specialize in reporting on how three key reproductive hormones (estrogen, testosterone and progesterone) affect women throughout their menstrual cycle, I get a steady line of requests from readers wanting to know how their hormone levels change when they’re pregnant. I usually give them general information, explaining that their estrogen and progesterone rise steadily.

But, that’s not the whole picture. The truth is, several key hormones involved with pregnancy rise. And now a study in the journal BMC Pregnancy and Childbirth provides a detailed graph charting exactly which ones and how high they get.

The study’s goal was to get a better understanding of how exposure to certain levels of hormones during pregnancy can impact the mother or child’s health immediately or in the future and to determine if hormone concentrations in the first two trimesters of pregnancy could predict hormone levels in the third.

To get this information, they examined blood samples of 71 women with healthy pregnancies through each trimester (weeks 10-12, weeks 20-22, weeks 35-37). They included women who were having their first child (primaparous) and second child (multiparous) and those who had two consecutive pregnancies to determine if there were any differences.

They charted what they found in the graph, which you can see here.

Here’s what they measured:

Estradiol: One of the three estrogens (estrodiol, estrone and estriol) produced in your body, this is the estrogen whose level rises and falls during your menstrual cycle and has the strongest impact on your moods, health and behavior during your cycling years. When I refer to “estrogen” in my Hormone Horoscopes and Hormonology Tips, I’m specifically referring to estradiol. After menopause, the level of this hormone drops significantly and stays low and steady. This estrogen is produced primarily in the ovaries and to a lesser extent by the adrenal glands and body fat.

Estrone: A weaker form of estrogen, it’s produced by the ovaries, placenta and body fat and is the predominant estrogen produced after menopause.

Progesterone: A hormone produced by the corpus luteum (what’s left over of the follicle after ovulation), it helps thicken the uterine wall.

Testosterone: Produced in small amounts in women compared to men, this hormone helps rev your sex drive and plays a role in helping maintain a pregnancy and develop male sex organs in a boy.

Prolactin: Produced in the pituitary gland (a small pea-sized protrusion in the base of your brain), this hormone enables you to make breast milk.

OPG and sRANKL: These two proteins–osteoprotegerin (OPG) and soluble receptor activator of nuclear factor kappaB ligand (sRANKL)–are involved in the regulation of bone resorption and bone mass and may play a role in birth length and birth weight.

As you can see in the chart above, the estrogens, progesterone, testosterone and prolactin rise throughout pregnancy–with the estrogens and prolactin having a steeper increase until week 22, then climbing more slowly. The proteins remain relatively stable in women with their first pregnancy and dip slightly in women with multiple pregnancies.

According to the researchers, during the first 9 weeks of pregnancy, estradiol, estrone and progesterone are churned out by the corpus luteum and to a lesser extent the ovary and adrenal gland. After that time, the placenta takes over and becomes the main source of these hormones.

Women who are pregnant with their second baby produce slightly less estradiol compared to their first pregnancy likely because the body metabolizes this hormone more efficiently in subsequent pregnancies. They also produce less progesterone and testosterone.

Curious if your  hormone levels can predict the sex of your baby? Though this study found no hormone differences whether the baby was a boy or girl, prior research is conflicting. Some found links, others didn’t so the jury is still out.

I hope this information helps you gain a better understanding of what happens to your hormones during pregnancy.

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