There’s no denying that the past two years have been tremendously tough on all of us. As the COVID-19 pandemic continues, more and more studies are being conducted on both the virus itself and the efficacy of the vaccine.

A recent scientific study published in the Obstetrics & Gynecology journal shows that the COVID-19 vaccine can cause very minor changes to the timing of menstruation (less than one day), and that the change is temporary — more akin to having a sore arm post-vaccine, rather than a serious adverse event.

The end result showed that periods were late by less than one day on average, and they returned to normal within one or two months post-vaccine.

The study was led by Dr. Alison Edelman, a professor of obstetrics and gynecology at Oregon Health and Science University, who notes to NPR.org that the results were “reassuring and also validating.”

While more research can be beneficial to the link between the vaccine and menstruation, the results show solid evidence that any effect of the COVID-19 vaccines on periods is small, temporary, and no cause for concern. Dr. Diana W. Bianchi, director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), adds that while this minor side-effect is “nothing to get alarmed about,” it does affirm what individuals had been reporting.

“It is reassuring that the study found only a small, temporary menstrual change in women,” Dr. Bianchi shares. “These results provide, for the first time, an opportunity to counsel women about what to expect from COVID-19 vaccination so they can plan accordingly.”

Worth noting is that menstrual cycles often change a small amount from month to month regardless. These temporary changes can be caused by a wide variety of factors including stress, lifestyle changes, and certain underlying health conditions. These minor changes are normal and do not have an affect on overall health or fertility.

We continue to recommend the COVID-19 vaccine to all of our patients — including those who are pregnant or plan to get pregnant.

Edelman echoes earlier reports that the vaccine has no effect on fertility or pregnancy. Moreover, the COVID-19 virus itself can have a profound effect on health.

“The risk of COVID-19 disease in pregnant women is incredibly serious,” said Edelman, who has watched pregnant women end up in intensive care because they’re not vaccinated.

Also, note that you can get the vaccine during your period; there is no need to reschedule.

More About the Study

Funded by the National Institutes of Health (NIH), the study of nearly 4,000 women aged 18 to 45 years old included a mix of unvaccinated and vaccinated individuals, with most of the vaccinated (55%) receiving the Pfizer vaccine and several others having received either Moderna or Johnson & Johnson. Vaccinated participants with normal cycle lengths (24–38 days) were monitored for three consecutive cycles before the first vaccine dose and then for another four to six cycles post-vaccine, while unvaccinated individuals were monitored for six cycles over a similar time period.

If you have any questions or concerns, please speak with your healthcare provider.