If you’re about to undergo in vitro fertilization (IVF), your healthcare provider likely prescribed estrogen to help you conceive. You might be surprised, especially if you’ve been told your body makes too much estrogen, but this is a common practice.

Read on to learn more about the benefits of estrogen treatment, the possible side effects, and why healthcare providers recommend women take Estrace (estradiol) during IVF.

What Is Estrogen?

Hormones are the body’s chemical messengers. They help control how cells and organs work. Your ovaries make most of your estrogen from fat molecules.

Estrogen kicks off puberty by making your breasts and pubic and underarm hair grow. It also controls your periods and helps with other body functions. For example, estrogen helps keep your mind and bones strong, regulates cholesterol levels, and prevents heart disease.

Your body makes three types of estrogen:

  • Estradiol: This type is active from puberty to menopause. It’s the strongest of the three. It controls your menstrual cycle.Estriol: Your body starts producing this type around the 8th week of pregnancy. It helps your uterus grow and prepares your body for childbirth.Estrone: Estrone is the weakest type of estrogen. It continues to be made after menopause and is present in higher amounts after menopause compared to other forms of estrogen.

How IVF Works

In vitro fertilization (IVF) is a procedure that helps people conceive. Fertility doctors stimulate eggs to grow, collect eggs from the ovaries, and then fertilize them with sperm to create embryos. Embryos can be transplanted back into the uterus to help someone conceive.

You can use your eggs and partner’s sperm. Or you can use eggs, sperm, or embryos (fresh or frozen) from a donor. A landmark IVF study published in 2003 found there’s a window of time when a woman’s uterus is receptive to a fertilized egg. Estrogen helps make this happen.

Estrogen levels naturally rise and fall during a woman’s menstrual cycle. Some of the medications women take during IVF cause estrogen levels to increase. In some cases, a doctor may use estrogen to prime the eggs before starting IVF.

Estrogen Before IVF

A review published in 2015 in Medicine analyzed 11 studies. It found that taking estrogen and progesterone improved the chances of clinical pregnancy compared to taking just progesterone.

Clinical pregnancy means the women’s pregnancy hormones rose, and healthcare providers confirmed a heartbeat on an ultrasound. Other outcomes, including miscarriage (pregnancy loss) rates, were the same.

Another analysis of 19 studies published in 2020 also found that taking both hormones improves early pregnancy chances.

Side Effects

Using estradiol for more than a year can increase your risk of blood clots, stroke, or heart attack. Estradiol has also been shown to increase the risk of cancer of the breast, uterus, or ovaries.

Fertility doctors sometimes prescribe estrogen for several days before a patient starts IVF to help synchronize the eggs and optimize stimulation. In frozen embryo transfer cycles, estrogen can be used to help thicken the lining of the uterus and prepare it for pregnancy.

However, these risks are lower if low doses are used for less than a year. Taking estrogen in combination with progesterone also helps offset the risks. Other possible side effects may include:

  • Light vaginal bleeding Upset stomachNausea, vomitingVaginal dischargeVaginal itchingWeight gainBloatingSwelling of the hands, feet, anklesHeadachesBreast tenderness or painSkin irritationRash

Do not stop taking estradiol before consulting with your fertility doctor first. This could affect your IVF cycle.

Summary

Fertility doctors prescribe estrogen to patients undergoing IVF to help stimulate the eggs to grow or during a frozen embryo transfer to help thicken the lining of the uterus and help increase the chances of embryo implantation. Estrogen supplements come in pills that you swallow or insert into your vagina, patches that stick to your belly, or injections that you inject into the muscle.

Most short-term side effects range from light vaginal bleeding to skin rash. If you take an estrogen-based medication and have symptoms that concern you, speak to your healthcare provider or pharmacist.