estrogen levels in pregnancy

What Is The Role Of Estrogen During Pregnancy?

Dr. Jolene BrightenPublished: Last Reviewed: Breastfeeding, Hormones, Pregnancy Leave a Comment

Estrogen is probably the most talked-about hormone in the female health world. It takes the blame for everything from acne to mood swings, but it also has an important job to do, especially during pregnancy. Throughout one pregnancy, a woman can produce more estrogen than she will over the rest of her life. This powerhouse hormone is essential in preparing her body to support a new life.

Whether you're pregnant, planning for pregnancy, or just curious, let's explore the many roles and changes of estrogen levels during pregnancy.

What Does Estrogen Do During Pregnancy?

During pregnancy, estrogen has many key effects. It helps develop the placenta and the network needed to bring nutrients and waste to and from the growing baby. For the fetus itself, maternal estrogen triggers the development of organs like the lungs, liver, and endocrine glands.

In the mother's body, increased estrogen levels help expand the uterus, maintain the uterine lining, and increase blood flow and vascularization (the formation of new blood vessels) in the uterus and placenta. 

Elevated estrogen also suppresses follicular stimulating hormone (FSH) and luteinizing hormone (LH), preventing ovulation during the pregnancy. 

Further into pregnancy, estrogen also promotes the production of milk and the growth of breast tissue, and prepares the body for birth and breastfeeding.

These elevated estrogen levels can have other effects as well. Hyperpigmented skin (usually temporary), and a stuffy nose during pregnancy are both estrogen-linked complaints. Because it triggers increased blood volume, estrogen can also add to spider veins, swelling, nausea, tender breasts, and more frequent trips to the bathroom (you know, in addition to the growing baby tap dancing on top of your bladder). 

Mask of Pregnancy – Melasma

Melasma, also called the “mask of pregnancy,” may be linked to estrogen, other hormones or potentially folate metabolism in pregnancy. Patches of light to dark brown skin can show up on the forehead, cheeks, chin, or anywhere on the face. Melasma is very common in pregnancy and in many cases it can resolve or reduce on its own following birth. Avoiding sun exposure and using sunscreen can help prevent the darkening of skin from worsening. 

Estrogen is also responsible for the darkening of your areolas, nipples, and other areas of your body.

Blotchy Skin?

Estrogen can be the reason your skin looks red and splotchy or you have patches of red dry skin.It causes an increase in blood flow and circulation which may be why you’re seeing more redness on your skin.

On the bright (radiant, in fact) side, many women experience a “pregnancy glow,” thanks to that increase in estrogen and blood flow to the skin.

Does Estrogen Maintain Pregnancy?

Estrogen works together with several different hormones to maintain a pregnancy, and estrogen is vital for a full, healthy term. Estrogen helps the uterus grow to accommodate the growing baby and maintains a well-functioning uterine lining and placenta. Estrogen plays a role in regulating other essential pregnancy hormones and in developing fetal organs.

How Is Estrogen Produced During Pregnancy?

A number of different tissues produce estrogen in the female (and male!) bodies, but estrogen in females is primarily produced by the corpus luteum in the ovaries. During pregnancy, however, the placenta mostly takes over, causing a steep increase in estrogen production. The primary form of estrogen in an ovulating woman is estradiol, while the placenta produces a form of estrogen called estriol.

Interestingly, estrogen formation is a team effort! Unlike the corpus luteum, the placenta is unable to convert cholesterol into estrogen. Instead, it uses an estrogen precursor produced by the fetus.

Estrogen Levels During Pregnancy Week By Week

Estrogen levels can vary widely during pregnancy and still be within a “normal” healthy range. The big takeaway is that estrogen will be much higher during pregnancy! During the third trimester, a mother's estrogen can reach over 6000 pg/mL. To put these values into perspective, the “hormonal rollercoaster” of a typical menstrual cycle only fluctuates between about 30-400 pg/mL!

Trimester 1Trimester 2Trimester 3
188-2497 pg/mL1278-7192 pg/mL3460-6137 pg/mL

Trimester 1 

Estrogen levels climb fast during the first trimester, and this rapid increase can make for an uncomfortable ride. “Morning sickness” is the period of nausea, vomiting, or sensitivity to smells and tastes that commonly strikes in early pregnancy. These effects are likely due to the sudden increase in hormones like estrogen, progesterone, and human chorionic gonadotropin (hCG). Pro-tip, ginger tea works wonders here!

During this period, the placenta takes over as the primary estrogen production source, as the corpus luteum begins to degenerate.

Trimester 2

During the second trimester, estrogen helps the mother prepare for breastfeeding. This includes enlarging the breasts and developing milk ducts. Estrogen is also triggering the development of hormones in the baby's body, including cortisol. While we might associate cortisol with stress in our bodies, it is crucial to help the fetus develop its lungs, liver, and other organs. 

Trimester 3

Estrogen levels keep on climbing throughout pregnancy, peaking in the 3rd trimester. This is when many mommas can experience extra water retention and swelling, thanks in part to all that excess hormone. Closer to delivery, estrogen is responsible for changes in the uterus and cervix that prepare them for contractions, dilation, and birth. 

If you notice excess fluid retention or swelling, try these tips and always communicate with your provider:

  • Increase foods rich in potassium like potatoes, avocados, acorn squash and spinach.
  • Avoid standing or sitting for long periods.
  • Avoid caffeine.
  • Rest often.

How Is Estrogen Testing Done?

Estriol (E3) is the main estrogen in pregnancy. During pregnancy, a doctor can use blood samples to monitor estriol levels, along with hCG levels, and alpha-fetoprotein. This test is usually performed around weeks 15-20 and can help identify risks for down's syndrome or other congenital disabilities. Doctors can also monitor estrogen levels through urine or saliva samples.

It's important to remember that healthy estrogen levels vary widely across pregnancy, so don't stress out over fluctuations. Your doctor will know when to take action. And for the most part, this isn't a test that needs to be performed as part of a healthy pregnancy.

What Happens If Estrogen Levels Are Low During Pregnancy?

Low estrogen levels are linked to lower fertility, increased risk of miscarriage and a woman with below-normal estrogen may have difficulty becoming pregnant. If you suspect hormones are slowing down your plans for pregnancy, grab the free 7-day Meal Plan to give your hormones what they need to find balance. 

During pregnancy, however, low estrogen is less common. Remember– there is a wide range of tolerance for “healthy” levels! 

Abnormally low estrogen levels during pregnancy don't mean anything by themselves, but together with other factors, can be signs of increased risk of preeclampsia, autism, or certain birth defects. Your doctor can help determine if further testing is needed. 

The Bottom Line

Estrogen is just one of several fascinating hormones that help support a healthy pregnancy. Throughout any phase in life, supporting your body's hormonal health helps your hormones to support you.

If you're looking to brush up on your hormonal health, start with my free e-book and Hormone Starter Kit with 7-day Meal Plan.

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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is one of the leading experts in women’s medicine and is a pioneer in her exploration of the far-reaching impact of hormonal birth control and the little known side effects that impact health in a large way. In her best selling book, Beyond the Pill, she shares her clinical protocols aimed at supporting women struggling with symptoms of hormone imbalance, including Post-Birth Control Pill Syndrome and birth control related side effects. A trained nutritional biochemist and Naturopathic Physician, Dr. Brighten is the founder and Clinic Director at Rubus Health, an integrative women’s medicine clinic. She is a member of the MindBodyGreen Collective and has been featured in prominent media outlets such as Forbes, Cosmopolitan, ABC news, and the New York Post. Read more about me here.