During the pandemic, many women were afraid to be vaccinated because of widespread misinformation that COVID-19 shots would harm their chances of getting pregnant.

But in a new study from Sweden, researchers found no statistically significant difference in rates of childbirth or miscarriage among vaccinated and unvaccinated women.

“Unsubstantiated rumors about side effects of COVID-19 vaccines still are circulating on social media,” said Toomas Timpka, MD, PhD, senior author of the paper, published last week in Communications Medicine, and a professor of social medicine and public health at Linköping University.

Although the study was not a randomized trial, the research “shows it is very highly unlikely that COVID-19 vaccines have any meaningful negative effect on fertility or childbirth rates,” Timpka told CIDRAP News.

Findings align with previous research

Researchers were able to analyze medicals records of nearly 60,000 women ages 18 to 45 in one Swedish county because the country’s national health system keeps detailed records of births, deaths, vaccinations, and other key data. About 75% of women in the study were vaccinated from 2021 to 2024. Among those who were vaccinated, 97% received an mRNA vaccine.

When comparing childbirth rates and recorded miscarriages between vaccinated and unvaccinated women, the researchers found adjusted hazard ratios of 1.03 for childbirth — meaning that vaccinated women were 3% more likely to give birth —  and 0.86 for miscarriages — suggesting that vaccinated women were 14% less likely to have a miscarriage. The team’s analysis suggests neither ratio is statistically significant, meaning that the findings could have been due to chance.

The findings align with “more than a dozen studies showing that COVID vaccination does not reduce the chance of conception,” said Viki Male, MD, an associate professor in reproductive immunology at Imperial College London, who was not involved in the study.

One of the strengths of the study is that it examined conception and pregnancy in the general population, Male said. Most previous research “focused on couples undergoing fertility treatment.”

The new study’s results are particularly compelling because of its large size and study design, Male said. Researchers adjusted their findings for factors other than COVID-19 that could have affected conception rates, such as age and underlying illness.

“This should further reassure women that COVID vaccination will not prevent them from getting pregnant or having a baby,” Male said.

Five years after COVID-19 vaccines became available, women continue to ask about whether the shots will affect their fertility, said Kevin Ault, MD, a professor of obstetrics and gynecology at the Western Michigan University Homer Stryker School of Medicine.

“Patients do ask about it, but it is easy to debunk these myths because of these well-done studies,” said Ault, who was not involved in the new study. “Sadly, I don’t think this misinformation is going to go away. It has been used for decades against several vaccines.”

Vaccines protect pregnant women and babies

Being infected with COVID-19 can be dangerous for pregnant women, who have a higher risk of being hospitalized than non-pregnant women.

Vaccination reduces that risk substantially, research shows.

A study published in December in JAMA found that pregnant women who develop COVID-19 after being vaccinated are much less likely to be hospitalized, need intensive care, or deliver early compared with women who aren’t vaccinated.

“Evidence is piling up that the vaccinations are safe, but that COVID-19 infection in pregnancy is not,” said Tara Smith, PhD, professor of epidemiology at the Kent State University College of Public Health, who was not involved in either study.

Timpka said there’s no doubt that women benefit from being vaccinated.

“Present scientific evidence is clear that the protection against severe disease a COVID-19 shot provides clearly outweighs possible risks,” Timpka said. “Women who want to start a family and who are on the fence about whether to get a COVID-19 shot should not hesitate about having the vaccine.”

Childbirth trends unrelated to vaccination

Rumors about COVID-19 vaccines and fertility have been fueled in part by widespread declines in birth rates during the pandemic, according to background information in the new paper.

In high-income countries around the world, birth rates fell during the pandemic, when many communities were locked down and suffering high rates of unemployment and inflation. Although birth rates rebounded after pandemic-era restrictions ended, rates dropped again in 2022.

This should further reassure women that COVID vaccination will not prevent them from getting pregnant or having a baby.

The US fertility rate—or the number of children born to women of child-bearing age—reached a record low in 2024, according to the Centers for Disease Control and Prevention (CDC).

The authors of the study wrote that there are “alternative and more plausible explanations” for the decline in births than COVID-19 vaccines, particularly pandemic-related social, economic, and behavioral changes.

US birth rates, for example, have been declining for nearly two decades.

Some of that decline reflects positive social trends, such as fewer teen pregnancies. Some research suggests that inflation may affect birth rates by making it more financially difficult to raise children.

Myths about vaccines continue to grow

Anti-vaccine activists have a history of blaming vaccines for fertility problems, Smith said. People opposed to vaccines have made the same charges against human papillomavirus (HPV) shots, tetanus shots, and polio vaccines.

“Fertility is such an easy target for people who don’t like vaccination and want to get rid of it,” Smith said. “Unfortunately, miscarriages do happen. Poor pregnancy outcomes can happen no matter what.”

Misinformation about COVID-19 and vaccines has increased because of mixed messages from the Department of Health and Human Services (HHS), Timpka said. 

While the American College of Obstetricians and Gynecologists recommends COVID-19 vaccinations for pregnant women, the Trump administration has flip-flopped on the issue.

In May of last year, two top officials at the Food and Drug Administration (FDA) wrote an article detailing plans to curtail access to COVID-19 vaccines for the general population while allowing them for people at higher risk of severe illness. The article, published in The New England Journal of Medicine, listed pregnancy as a high-risk condition.

Fertility is such an easy target for people who don’t like vaccination and want to get rid of it.

A few days later, HHS Secretary Robert F. Kennedy Jr. announced that the CDC had stopped recommending COVID-19 shots for children and pregnant women. 

In September, the Advisory Committee on Immunization Practices, which gives recommendations to the CDC, recommended that COVID-19 vaccines should be available to anyone 6 months and older based on “individual decision-making.”

With so many conflicting messages, Smith said it’s easy to understand why women would be confused and hesitant to accept vaccines.

“I don’t think the study is going to dispel those myths, unfortunately, because that’s not really how myths get dispelled,” Smith said. “It’s not an evidence-based thing.”

Public attitudes about vaccines, she said, “tend to be based on vibes and feelings.”