COVID-19 may decrease male fertility. Here's what you need to know.

The Biden administration has struggled to persuade more Americans to get boosted before a potential fall-winter COVID-19 surge, but anyone hoping to have a baby in the near future may want to make sure they’re protected. While there is no evidence that vaccines affect a person’s ability to get pregnant, a study published earlier this year did find that contracting the virus might impair fertility — at least temporarily.

The study, which was funded by the National Institutes of Health (NIH), found that couples in which the male partner had tested positive for SARS-CoV-2 within 60 days were 18% less likely to conceive during that menstrual cycle than those who had not tested positive. After 60 days, there was no difference in conception rates.

More than 2,000 U.S. and Canadian couples participated in the study, with researchers analyzing data from the Pregnancy Study Online, an internet-based study led by Boston University of couples trying to conceive without fertility treatment. Participants, all of whom identified as female and were 21 to 45 years old, completed questionnaires on their lifestyle and medical histories, including whether they or their male partners had tested positive for SARS-CoV-2. Participants invited their partners to complete a similar questionnaire.

Why might COVID-19 affect male fertility?

While the study showed a difference in conception rates among those who had recently tested positive, more research is needed to explain why the virus may affect fertility.

“Unfortunately, the study wasn’t designed to answer that question,” Dr. Esther Eisenberg, a reproductive endocrinologist with NIH, told Yahoo News. “The data just showed what the level of fertility was, and that it was lower in couples in which the male contracted COVID. One can speculate, but we would have to do another study in order to find those reasons.”

The study did point out that fever, which is known to reduce sperm count and motility, is also a common symptom of COVID-19 and could explain the temporary decline in fertility. The effects of fever on sperm concentration, motility and morphology, the study says, can persist for three to four months. However, a short-term reduction in sperm count is possible after a fever from any illness — or any considerable increase in body temperature — not necessarily from COVID-19 in particular.

“Anything that increases the temperature under which the sperm are produced — so sitting in a hot tub for a long period of time more regularly, being out in the heat, very hot weather — all those things could impact the sperm count and motility,” Eisenberg said.

“But it doesn’t happen to everyone,” she added. “Some individuals might be more prone to having this happen than others.”

Researchers involved in the study also identified inflammation in the testes and nearby tissues and erectile dysfunction — “all common after SARS-CoV-2 infection”— as possible reasons for a decline in fertility. A study published last year found that 10% to 22% of men with acute COVID-19 infection developed testicular swelling or inflammation, while COVID-positive Italian men in another study published last year self-reported 20% higher instances of erectile dysfunction than COVID-negative participants.

A study published in September, which reviewed 26 articles and data on how COVID-19 affects male fertility, also observed a “significant difference” in semen quality and sex hormone levels among COVID-positive patients. Semen quality and sex hormone levels gradually increased to normal as patients recovered.

Eisenberg noted that any illness may temporarily affect one’s fertility — “but if it’s a temporary illness, then long-term your fertility and conception is not affected because you recover, and then you recover your ability to get pregnant.”

She added that there could also be a much simpler explanation for why conception rates were lower among COVID-positive men.

“If I speculate, it could be that the couples were so sick they didn’t have sex — and if you don’t have sex, you can’t get pregnant,” Eisenberg said. “I think that might be one of the main ways that couples could have reduced pregnancy, especially if the male was sick during the time that the woman was fertile.”

The takeaway

The NIH-funded study also looked at how COVID-19 vaccines might affect a couple’s chances of conceiving, and concluded that vaccination “does not impair fertility in either partner.” Given the risks of contracting COVID-19 while trying to conceive, as well as the dangers that COVID-19 infection poses to pregnant women and fetal health, researchers said their results could provide valuable information for anyone hoping to get pregnant who may be debating whether to be vaccinated.

Still, with breakthrough cases common even among fully vaccinated people, Eisenberg said anyone concerned about COVID-19 and its impact on fertility “should take the long view.”

“I think COVID is a serious illness, and I think one should take it seriously,” she said. “On the other hand, it does not overall impact your future fertility, and it does not overall impact your ability to get pregnant — which is good news.”