Two recent studies have found small but reversible changes in menstruation following COVID-19 vaccination, according to a review of recent data published in the BMJ.
“I wrote an editorial in the BMJ last September calling for more research to be done into reports that people were noticing changes to their menstrual cycles following vaccination,” Victoria Male, PhD, a lecturer of reproductive immunology at Imperial College London, told Healio. “That editorial got a lot of attention, so I felt a responsibility — now the research has been done — to come back and tell the readers of the BMJ what it found.”
In her review, Male discussed findings from a study by Alison Edelman, MD, MPH, and colleagues in Obstetrics & Gynecology, which showed that patients who received their first dose of a COVID-19 vaccine had no change in the start of their next cycle, whereas the second dose was associated with a half-day delay.
Victoria Male
“Among [patients who received two doses within one cycle], 10.6% experienced a change in cycle length of more than 8 days, which is considered clinically significant, compared with 4.3% in the unvaccinated cohort,” Male wrote of their findings. “In all groups, cycle lengths returned to normal by two cycles after vaccination.”
Male also mentioned a study from the Norwegian Institute of Public Health that “identified heavier than normal bleeding as the change most associated with vaccination.”
“Until I saw these results, I was completely on the fence as to whether there would be a real change associated with vaccination, or whether people were just noticing and discussing normal variation in their menstrual cycle in a way that they wouldn’t usually,” Male told Healio. “What I think is interesting, though, is that these two studies identified delays and heavier periods following vaccination, and these were precisely the changes that were most commonly reported anecdotally, and to post-marketing surveillance schemes like Yellow Card,” which is run by the Medicines and Healthcare products Regulatory Agency in the United Kingdom.
Moving forward, Male said more studies are needed to solidify these data, as well as to look more closely at certain subgroups of patients.
“These results are reassuring, but one thing I’m asked a lot is whether people with certain gynecological conditions, like endometriosis or [polycystic ovary syndrome], might be more vulnerable to these changes,” she said in the interview. “It would be good to see work that specifically addressed this issue, so that people with these conditions could feel more comfortable in making their decision about getting vaccinated. I think we also need to know more about how COVID infection affects menstrual cycles, as this will also play into the decision about vaccination for many people.”
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