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Pregnancy Hormones - Estrogen

So far we’ve covered the hormones progesterone and relaxin on the blog. Now, let’s look at estrogen—another key pregnancy hormone. What is it? What does it do?

Estrogen, like progesterone, increases suddenly and significantly during pregnancy.

A woman will produce more estrogen during her 40 weeks of pregnancy than she will all the non-pregnant weeks of her life combined!

This hormone supports a baby’s development in three ways: forming the baby’s blood vessels, helping nutrients flow from mother to baby, and supporting the uterus and placenta. Interestingly, the placenta, ovaries, liver, muscle, bone, and brain all produce estrogen during pregnancy.

Also the key hormone in milk duct development, estrogen enlarges the breasts during the second trimester and prepares the milk ducts for nursing. Estrogen is at its highest in the third trimester, and it prepares the uterus and cervix for contraction, dilation, and birth.

Estrogen can also cause some discomforts throughout pregnancy, as we’ve seen with other hormones. The sharp increase in the first trimester may cause nausea in some women. It may loosen ligaments, which (along mom’s growing breasts and belly) can cause back pain or a changing sense of balance.

Estrogen works on mom and baby’s vascular system, often giving women their pregnancy “glow”! As a result, it can also cause hyperpigmentation (of nipples, armpits, or belly) and melasma—brown patches on nose, cheek, and forehead—as it generates extra blood flow to the skin. It will take time but these skin changes will return to normal after the baby is born.

It is so helpful to know what to expect throughout the weeks and months of pregnancy. Tennessee Family Doulas’ Childbirth Education class answers your questions (especially, “Is this normal?”) and prepares you to make the decisions that are best for you during labor, delivery, and the early days at home.


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