Medical staff and volunteers prepare shots of the Moderna Covid-19 vaccine (PA)
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A study shows that COVID-19 vaccines can make women’s periods last longer, coming months after another paper found the shots are linked to increased menstural bleeding.
In a study published Sept. 27 in the British Medical Journal, researchers documented how COVID-19 vaccines can alter menstrual cycles and how long the impact could last.
A team of researchers led by Dr. Alison Edelman, professor of obstetrics and gynecology at Oregon Health & Science University, analyzed about 20,000 vaccinated and 5,000 unvaccinated women around the world. They obtained their data from a period-tracking app called Natural Cycles.
The team found that any COVID-19 vaccine can extend the menstrual cycle. Women who got the shot experienced approximately a one-day delay in getting their periods, compared with women who did not.
“These findings provide additional information for counseling women on what to expect after vaccination,” said Diana Bianchi, the head of the National Institute of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, said in a news release. “Changes following vaccination appear to be small, within the normal range of variation, and temporary.”
The study did not say why COVID-19 vaccines appear to be affecting the menstrual cycle. Edelman told The Washington Post that the immune and reproductive systems are connected and said that post-vaccine inflammation could be the cause.
Researchers noted that the study did not include women who were taking birth control pills, were between the ages of 18 and 45, and had regular menstrual cycles before getting the vaccine.
On average, vaccinated women experienced a 0.71-day increase after the first shot and a 0.56-day increase after the second. Those who got both doses in a single menstrual cycle had a 3.91-day increase in the cycle length, researchers found.
Women who were younger and who had longer cycle length before they got vaccinated were more likely to experience an increase, the study said.
With the latest study, its authors called for more research on how vaccines affect menstrual cycles or bleeding. Studies are needed to determine why vaccines can make such impacts, they added.
Increased Bleeding
It comes several weeks after a study linked increased menstrual bleeding to COVID-19 vaccines. In July, published in Science Advances, researchers found that 42 percent of respondents reported bleeding more heavily than usual after receiving the shot.
“We focused our analysis on those who regularly menstruate and those who do not currently menstruate but have in the past. The latter group included postmenopausal individuals and those on hormonal therapies that suppress menstruation, for whom bleeding is especially surprising,” Kathryn Clancy, a professor of anthropology at the University of Illinois Urbana-Champaign, said in a statement about the study.
Last month, top federal COVID-19 adviser Anthony Fauci drew flack from doctors after he told Fox News about reported COVID-19 vaccine-linked menstrual irregularities.
“The menstrual thing is something that seems to be quite transient and temporary,” Fauci told Fox News on July 25. “We need to study it more.”
That drew rebuke from Dr. Christiane Northrup, a former fellow in the American College of Obstetricians and Gynecologists.
“Unfortunately, the menstrual problems we are seeing are far from transient and temporary,” she told The Epoch Times in August. “Many women have been bleeding daily or having heavy, irregular, painful periods for an entire year.
Zachary Stieber contributed to this report.
