Pregnancy is an extraordinary time that brings many changes to a pregnant mother. To initiate and maintain the complicated pregnancy process, a woman’s body will become inundated with nearly a dozen hormones for which estrogen brings about substantial changes.

Besides progesterone, estrogen is the hormone that plays the biggest role in creating a baby. So while each of the hormones involved in a pregnancy are responsible for a particular function, estrogen and progesterone have the responsibility of regulating and initiating other hormones.

Normally, estrogen is associated with developing female sexual traits as well as starting and regulating a woman’s menstrual cycle. Not only that, estrogen helps keep bones healthy and cholesterol levels under control. But once a pregnancy begins, estrogen takes on entirely different characteristics and functions in a woman’s body.

During a pregnancy, a woman’s estrogen levels skyrocket during the first 12 weeks of pregnancy, increasing by more than 100 times. In fact, a woman will produce more estrogen during a single pregnancy than a lifetime of not being pregnant. Usually formed in the ovaries, a pregnant mother will start creating estrogen in the placenta to help maintain a healthy pregnancy.


High levels of estrogen are important for maintaining pregnancy and preventing miscarriage, and stimulates the hormonal processes necessary for fetal maturation. Estrogen aids pregnancy by:

• Helping the uterus grow

• Maintaining the uterine lining: Increased estrogen allows the uterus and placenta to create new blood vessels and transfer nutrients to your baby.

• Regulating other key hormone levels

• Triggering the development of baby’s organs

During the second trimester, estrogen plays a major role in the development of milk ducts that enlarges the breasts and encourages milk to flow

The increase in estrogen during pregnancy enables the uterus and placenta to:

• Improve vascularization (the formation of blood vessels)

• Transfer nutrients

• Support the developing baby


But these changes aren’t limited to accommodating the fetus. The effects of estrogen in pregnancy will also bring changes to the mother herself. As estrogen levels plateau by the end of the first trimester, elevated estrogen levels may be responsible for:

Spider veins: By relaxing the walls of blood vessels in your body, estrogen can cause an increase in blood flow that promotes the development of varicose veins/spider veins.

Nausea: Usually occurs during the first trimester due to spikes in estrogen. Morning sickness affects up to 70% of pregnant women.

Skin changes: Estrogen increases blood flow that can cause your skin to have a red, itchy complexion as well as acne. It can also cause hyperpigmentation, resulting in darker nipples and melasma as well as brown patches on your nose, cheeks and forehead.

Stuffy nose An increase in blood volume is also responsible for causing swollen mucous membranes.

Swelling: As estrogen levels rise throughout a pregnancy, pregnant women experience swelling in ankles, fingers, and feet during the final trimester.

Back pains: Estrogen will cause your body’s ligaments to soften, thereby putting pressure on your lower back and pelvis.

Achy breasts: The increased blood flow that babies need for nourishment also causes breasts to feel achy and tender.


For some lucky women, raised estrogen levels can result in a “pregnancy glow” that makes your skin look younger and healthier. In addition to progesterone and human chorionic gonadotropin, estrogen can cause a pregnant woman to have fuller lips, thicker hair, and stronger nails, and fuller breasts, all changes that will revert back to normal once the pregnancy is over.

One of the biggest effects of estrogen in pregnancy are mood swings. However, despite estrogen’s close associated with serotonin, the brain chemical associated with happiness, the connection is not yet fully understood by doctors. It is believed that changes in estrogen levels cause mood imbalances, of which anxiety and irritability are commonly experienced.

Estrogen is so important to a pregnancy that insufficient amounts can prove to be dangerous to the fetus. Low estrogen levels during pregnancy can lead to:

• Miscarriages

• Fewer eggs in the female babies born of the pregnancy

• Fertility issues in the female babies born of the pregnancy


One important thing to keep in mind is that estrogen and progesterone levels drop dramatically in the postpartum phase, returning to their pre-pregnancy levels within 24 hours after childbirth. 

In fact, because it can hinder your body from producing milk, your body will reduce estrogen levels when you are breastfeeding.

Here’s a comprehensive list of hormones involved in a normal pregnancy:

• Follicle stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Human chorionic gonadotropin (hCG)

• Estrogen

• Progesterone

• Relaxin

• Placental growth factor

• Human placental lactogen (HPL)

• Oxytocin

• Prolactin

Hormones during pregnancy have a complicated process of give and take. Human chorionic gonadotropin (hCG) is needed to transfer essential nutrients to the fetus during the early pregnancy, but by week 8-11, this job is taken over by estrogen and progesterone.

Meanwhile, estrogen promotes the growth of luteinizing hormone, which in turn stimulates the corpus luteum to produce progesterone, a key hormone that is required to support the early stages of pregnancy once fertilization occurs.

In all, the effects of estrogen in pregnancy are as complicated as they are unique to each mother. Prepare for your childbirth by finding out more about estrogen and hormones during pregnancy!

Are you expecting a baby soon? Are you looking for pregnancy-related services? Come to The WOMB Vaughan! We offer everything from Doula Support to Breastfeeding Support to classes and workshops!

Looking for more information? Read our blog to learn how to massage out a clogged milk duct, or discover the benefits of chiropractic care on fertility.

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