Estrogen and COVID-19: How Pregnancy, Birth Control Can Increase Risk of Blood Clots


New research has found that women who are pregnant or take estrogen either through birth control or hormone replacement therapy (HRT) may have a higher risk of developing blood clots if they contract COVID-19.

Though estrogen does not cause blood clots, if used in birth control or HRT it can increase a person’s risk by three- or fourfold. COVID-19 may exacerbate that risk.

Many COVID-19 patients in the intensive care unit (ICU) are developing blood clots that may contribute to respiratory failure.

Clotting with COVID-19 has been more common in patients who are older, male or have diabetes or obesity.

Some women who contract COVID-19 may need to discontinue their estrogen medications or begin anticoagulation therapy, according to the study, which published in the journal Endocrinology on Wednesday (December 2020).

According to the study, there have been no reports of increased incidence of venous thromboembolic events (VTEs) in pregnant women or people taking estrogen with COVID-19. Doctors have observed vascular abnormalities in the placenta of pregnant women with COVID-19.

Health experts say we need more research to fully understand how gender influences a person’s risk for severe COVID-19. Interestingly, women are generally less likely to die from COVID-19 compared to men, though it’s unclear as to why.

“My sense is, as with everything related to COVID, we are just beginning to understand gender as a risk for poor outcome in COVID and multiple factors are important, not just estrogen and clotting,” says Dr. Don L. Goldenberg, a rheumatologist and emeritus professor of medicine at Tufts University School of Medicine.

COVID-19 causes abnormal clotting

Several people who have been hospitalized with severe COVID-19 have developed blood clots.

VTEs are commonly reported in ICU patients — one found that 31 percent of ICU patients with COVID-19 experienced thrombotic complications.

Dr. Hamid Mojibian, a Yale Medicine interventional radiologist specializing in image-guided cardiac procedures, says there are a number of reasons COVID-19 may lead to clotting in some people.

Research has found that COVID-19 causes widespread inflammation in the body which may affect how well our platelets which are tiny blood cells that help regulate clotting — work and make them more prone to forming dangerous blood clots.

“Factors like overwhelming inflammation, vascular injury, platelet (blood cell) dysfunction, and pure immobility (stasis) contribute to blood clot formation,” Mojibian said.

Larger blood clots can prevent blood from flowing throughout our body and getting where it needs to be.

“During this pandemic, vein experts have found clots in the aorta, renal arteries, legs, and the brain,” says Mojibian.

Anytime blood supply is interrupted, there can be severe consequences, such as a stroke.

What is it about estrogen?

According to Goldenberg, estrogen is known to increase a person’s risk of VTEs.

With HRT and oral contraceptives containing estrogen, the risk of clots is highest in the first year of use amongst women with coagulation abnormalities.

Women without these abnormalities are also at higher risk for blood clots while taking these medications.

Estimates suggest 1 in 3,000 women who take birth control pills will get a blood clot each year.

Pregnancy, which causes the body to naturally produce more estrogen, is also linked to blood clots.

In fact, research shows the risk of venous thrombosis is six- to tenfold greater among pregnant women compared to nonpregnant women of the same age.

“Estrogen increases the gene expression of certain clotting factors and lowers factors which prevent blood clots. Overall, this leads to a ‘pro’ clotting state,” says Dr. Minisha Sood, an endocrinologist at Lenox Hill Hospital in New York City.

Evidence also suggests that estrogen impacts the immune system.

“Estrogen affects immune response and T cells as well as ACE-2 receptors, each important in COVID infection and severity,” says Goldenberg.

How can you cut your risk?

It may take some lifestyle changes, but health experts say it is possible to cut your risk of experiencing a clot.

Per the researchers findings, women who take birth control pills or HRT and get sick with COVID-19 may want to ask their doctor about alternative options that do not contain estrogen.

Sood doesn’t recommend discontinuing birth control or HRT as a preventative measure. If women taking these medications were to become severely ill with COVID-19, then it’s time to consider other options.

“There are still no firm guidelines but women not infected who are on HRT or oral contraceptives should consult with their physician regarding potential risk during the pandemic,” says Goldenberg.

Mojibian also recommends getting physical exercise as staying home and not moving increases your risk of venous thrombosis.

Quitting smoking can also help lower the risk as can a diet low in saturated fat and trans fat.

The bottom line

New research has found that women who are pregnant or take estrogen either through birth control or hormone replacement therapy may have a higher risk of developing blood clots if they contract COVID-19. Blood clots are a common complication reported in severe cases of COVID-19.

Some women who contract COVID-19 may want to discontinue any estrogen medications to cut their risk of clots, but it’s crucial to first consult a doctor.


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