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No evidence that COVID-19 vaccines cause infertility

A pregnant woman smiling at a laptop.

There's a story going around that COVID-19 mRNA vaccines may cause infertility. But here's what women should know: There's no evidence that either the Pfizer or Moderna vaccine interferes with fertility or pregnancy.

What's behind the myth?

These two vaccines teach the immune system to make antibodies that attack the coronavirus's spike protein. But some people raised concerns that the antibodies might mistake their target.

There's a protein called syncytin-1, which helps a fertilized embryo attach to the placenta. A portion of that protein is similar to the virus's spike protein.

If the antibodies were to mistakenly attack syncytin-1, the theory goes, it could cause an embryo to detach from the placenta. This would cause a miscarriage.

What are the facts?

The spike protein created by vaccination is structurally different from syncytin-1, according to the Infectious Diseases Society of America. Neither of the vaccines contains syncytin-1. And there is no evidence that the antibodies created by the vaccines target syncytin-1.

Moreover, in clinical trials of the vaccines, women who received the vaccines were just as likely to get pregnant during the trial as women who received a placebo. And no women in the vaccine group experienced miscarriages.

Also, when someone gets COVID-19, the body produces its own antibodies that target the spike protein. Experts say if these antibodies were able to attack the placenta, they'd expect to see a rise in miscarriages in people who've had COVID-19. But there's no evidence of that.

Should pregnant women get the vaccine?

Pfizer began a global study in February to evaluate its vaccine in pregnant women. Separately, a New England Journal of Medicine review of more than 35,000 pregnant women who received the Pfizer or Moderna vaccine found no safety concerns. More studies are planned.

In the meantime, women who are or want to get pregnant should talk with their doctor about the pros and cons of getting a COVID-19 vaccine. They should consider:

  • How active COVID-19 is in their community.
  • Their personal risk of getting COVID-19.
  • The risks COVID-19 would pose to them and their fetus.
  • How well the vaccine works.
  • The side effects of the vaccine.
  • What is known so far about the vaccine and pregnancy.

To learn more about vaccine safety, visit our Coronavirus health topic center.

Reviewed 6/21/2021

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