How does Covid-19 infection and vaccination affect pregnancy and fertility?

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Efforts to immunise populations against Covid-19 have faced persistent online rumours that vaccination affects fertility or pregnancy.

Despite a lack of evidence that jabs reduce the chances of becoming pregnant, increase the risk of miscarriage or cause related forms of harm, misinformation has continued to spread on the web.

Here we look at what recent studies have concluded on vaccination and Covid-19 infection in relation to pregnancy and fertility.

Why have there been suggestions that Covid-19 vaccination could affect pregnancy?

One factor, said Ian Jones, a professor of virology at the University of Reading in the UK, is that there was little data available early on about pregnancy and the vaccines that were available.

“In the early stages, the trials were not targeted at pregnant women,” he said.

“So the data simply wasn’t good enough to say clearly the vaccine was safe. That’s true of all vaccines when they’re released, so there’s a general feeling new vaccines should only be used cautiously with pregnant women.”

The vaccines have since been used on “huge numbers” of pregnant women, so he said that doctors could now say that the Covid-19 vaccines were “completely safe for pregnant women to take”.

Among other studies, research from Norway released in the New England Journal of Medicine in November found that Covid-19 vaccination did not make miscarriage more likely.

England's National Health Service recommends that pregnant women are given the Pfizer-BioNTech or Moderna vaccines ahead of the Oxford-AstraZeneca jab, “because these [Pfizer-BioNTech and Moderna] vaccines have been more widely used during pregnancy in other countries and no safety concerns have been identified”.

What have studies found regarding fertility?

Among other research, a study published in January by the Boston School of Public Health found that fertility of women and men was not harmed by Covid-19 vaccination.

In the research, published in the American Journal of Epidemiology, scientists found that being given the Pfizer-BioNTech, Moderna or Johnson & Johnson vaccines did not affect the chance of conception.

According to Prof Jones, suggestions that fertility may be affected by vaccination is “anti-vax stuff” that circulates on chat boards, but “doesn’t have any validity at all.”

While there is no evidence that vaccination reduces fertility, the same study indicated that Covid-19 infection may temporarily reduce fertility in men.

A reduction in fertility was found only in men who had tested positive within the previous 60 days, but not in those who had had an earlier infection, indicating that the effect is not permanent.

Previous studies also indicated that contracting Covid-19 could negatively affect male fertility.

How can Covid-19 affect pregnancy?

While it has been established that coronavirus vaccines do not reduce the chance of woman falling pregnant or increase the risk of miscarriage, a Covid-19 infection during pregnancy can prove harmful.

A study published in Nature Medicine in January based on results in Scotland reported that among women who had given birth within 28 days of a Covid-19 diagnosis, the baby mortality rate was increased four-fold.

“All baby deaths after Covid-19 in pregnancy occurred in women who were unvaccinated,” said Dr Sarah Stock, a reader in maternal and foetal health at the University of Edinburgh and the study’s first author.

Unvaccinated women were also more likely to be admitted to hospital and to be treated in an intensive care unit.

Further research has found that Covid-19 increases the risk of premature birth and of stillbirth.

“There is very convincing evidence from around the globe that vaccination before or during pregnancy is the safest and most effective way to protect pregnant women and their babies against Covid-19 infection and the serious complications that Covid-19 can cause,” said Dr Stock.

“If you are at any stage in pregnancy, or hoping to become pregnant, I would encourage you to get vaccinated to protect you and your baby.”

A separate study released at the end of January based on research at Boston Medical Centre indicated that the placenta may prevent many pregnant women with Covid-19 from passing the infection to their babies.

The researchers found that in the placentas of women with Covid-19, there were lower levels of ACE-2, a cell receptor that allows the coronavirus to enter cells. This could prevent SARS-CoV-2 being passed to the foetus.