On September 27, 2022, a large study published in BMJ Medicine confirmed the findings of previous research that linked COVID-19 vaccination with a temporary average increase in menstrual cycle length of less than one day. For study participants who received only one vaccine dose per cycle, the number of days in a cycle had returned to pre-vax lengths in the cycle after vaccination. There was a larger increase in cycle length, almost four days, for individuals who happened to receive two doses of a vaccine within the same cycle. The research, funded by the National Institutes of Health, included 20,000 people from the United States and other parts of the world who received any of nine different vaccines. Earlier this year, a similar study of about 40,000 people was published in the July 15 issue of the journal Science Advances. Researchers found that about 42 percent of menstruating survey respondents reported a heavier menstrual flow after receiving the COVID-19 vaccine. But not everyone was affected: Roughly an equal number of people, about 44 percent, reported no change to their menstrual flow after the vaccine, and around 14 percent saw a lighter flow. Of the respondent who don’t typically menstruate, breakthrough bleeding was reported by 71 percent of people on long-acting reversible contraceptives and 66 percent of postmenopausal people. RELATED: Stopping Menstrual Periods Is Safe, Experts Say The survey included individuals with a range of gender identities, such as transgender, nonbinary, or gender-fluid. The researchers discovered that, of 552 respondents who said they used testosterone or other gender-affirming hormones and did not usually menstruate, one-third reported breakthrough bleeding after they received a COVID-19 vaccine, 9 percent reported chest or breast soreness, and 46 percent reported having other symptoms they would usually associate with a period, such as cramping and bloating. The study did not report the percentage of respondents who experienced breakthrough bleeding before vaccination, and it’s important to note that menstruation is not always reliably suppressed with these therapies. The team is currently conducting a follow-up survey to see if these symptoms are temporary or long-lasting. A coauthor of the study, Katharine Lee, PhD, a postdoctoral research scholar in the division of public health sciences at Washington University in St. Louis, suspects the culprit for these changes is the immune and inflammatory response triggered by the vaccine. “There is a huge mobilization of your immune system. And I think it could just be a little bit of cellular cross-talk that is disrupting this process.”
How Your Period Responds to Stress
And what if you noticed menstrual changes after you caught the virus or even if you didn’t catch it? That is also quite possible. Sometimes stress alone can throw your period out of whack, and if you’re someone who’s usually very regular, even slight differences are noticeable. And in case you need any convincing, there’s no question that the coronavirus pandemic and other distressing developments in recent history qualify as a major form of stress. Apart from the illness caused by the disease itself, the pandemic has brought the kinds of intense personal challenges that can really disrupt lives, whether that’s losing a loved one, managing remote work for yourself or schooling for kids, or getting divorced. RELATED: Roe Struck Down, Formula and Tampon Shortages: Are You Feeling Overwhelmed? So it’s not exactly surprising that some people who menstruate have been experiencing disruptions — from skipped periods to longer cycles to changes in bleeding patterns. This can happen if someone becomes infected with the novel coronavirus or if they’re simply dealing with the prolonged stress of the pandemic, according to a report published in June 2020 in MedPage Today. “What we can say about COVID-19 and its effects on the menstrual cycle is comparable to what we can say about other viral infections and prolonged periods of stress — menstrual disruptions are likely to occur,” says Taraneh Shirazian, MD, the director of global women’s health and an assistant professor of obstetrics and gynecology at NYU Langone Health in New York City. “If you get COVID-19, it’s a stress on the body and a major stress on the hypothalamic pituitary adrenal (HPA) axis,” which is the body’s central stress response system. During times of stress, the HPA axis stimulates the release of the stress hormone cortisol to help the body prepare to fight or flee from a threat. With ongoing stress, “increased cortisol levels can affect a woman’s menstrual cycles,” Dr. Shirazian says. In addition, with prolonged periods of stress, the stress response system can burn out, and the HPA axis can be suppressed, which drives down the pituitary production of follicle stimulating and luteinizing hormones (FSH and LH), which then drive down ovarian production of estrogen and progesterone. With complete suppression of the HPA axis, a woman may experience amenorrhea, the absence of periods. With partial suppression, a woman could have spotty periods or periods of bleeding every few weeks. “There isn’t one clear pattern we can expect — women respond differently to suppression of the HPA axis,” Shirazian says. It’s important to remember that “biologically, women menstruate for one reason and one reason only — to get pregnant,” Dr. Streicher adds. The dysregulation of the menstrual cycle that may be induced by COVID-19 infection may be a biological and evolutionary protective mechanism, both for the woman and for her potential offspring. As far as the stress of the pandemic goes, it’s occurring on two fronts. Besides the fact that stress itself increases cortisol levels, which can affect menstruation, the disruptions that have occurred in people’s lifestyles and routines during the pandemic can affect a woman’s menstrual cycle. And if women have become more sedentary or gained weight during the pandemic, Shirazian notes, these changes can affect their periods, perhaps leading to missed menstrual periods, longer spans between periods, or longer bleeding time. RELATED: National Period Action Day Indeed, “any stressful situation can alter hormone levels and cause someone not to menstruate regularly,” Streicher says. “Mostly it’s because ovulation is not occurring.”
Even More Menstrual Cycle Disruptions for Women With Endo or PCOS
Evidence from a study published in MedRxiv, which included about 1,200 women with records of their menstrual cycles and vaccination dates, showed that people with a preexisting diagnosis of endometriosis or PCOS were more likely to notice disruptions to their cycle than people without those diagnoses. “That could suggest that, in some people who are already vulnerable to cycle disruptions, the vaccines could be having an effect,” says Victoria Male, PhD, one of the study authors and a lecturer in reproductive immunology in the department of metabolism, digestion, and reproduction at Imperial College London’s Chelsea and Westminster Hospital Campus. RELATED: Is Your Period Normal?
No Sign of Fertility Impact From the Virus or Vaccines
Dr. Male’s study found no effect on fertility. “Even if there is an effect of cycles … it doesn’t seem to be doing anything to fertility. In fact, in our study, 36 of the participants became pregnant in the same cycle they were vaccinated or the cycle after,” she said.
Taking Back the Monthly Menstrual Period
Whether or not you have been sick with COVID-19 or received a vaccine, if you experience a change in your periods during the pandemic, the first step is to consider whether you could be pregnant. If you confirm that you’re not expecting and “you miss a period for a month or two but you’re otherwise feeling fine, it’s not something to panic about,” Streicher says. Additional reporting by Monroe Hammond and Stacey Colino.
