More than 4 in 10 Women Experience Menstrual Changes After COVID-19 Vaccination: Peer-Reviewed Journal 'Cureus'

"There is an increased incidence of changes in menstrual cycle after COVID-19 vaccination, particularly in menstrual cycle length, menstrual pain, and the flow of menstruation," the study reads.

A new study published Tuesday in the peer-reviewed journal Cureus has confirmed 41% of women experience menstrual disruptions after receiving a COVID-19 vaccine.

That number increases to 44.1% after a second dose.

“The study found that 41.7% (223) of women experienced menstrual changes after the first dose of the COVID-19 vaccine, increasing to 44.1% (236) after the second dose,” the study reads.

Significantly, these women had “no history of menstrual irregularities before receiving” a coronavirus vaccine.

The researchers “aimed to explore the menstrual irregularities following COVID-19 vaccination in Saudi women of childbearing age.”

A total of 535 participants completed an online questionnaire via Google Form “about any menstrual irregularities they experienced after receiving the COVID-19 vaccine.”

More than half of the participants were between 17- and 30 years old, 31% of participants were aged between 31 and 45 years, and less than 10% of participants were aged more than 45 years.

The authors emphasized the incidence dysmenorrhea (painful menstrual periods) “increased slightly from 30.9% to 32.2% after the two doses.”

The incidence of heavier menstrual flow also “increased from 26.9% to 30.5%,” while the incidence of lighter menstrual flow “decreased from 26.9% to 24.6% after the first and second doses.”

The study underscores how the incidence of increased duration of the period, late period, and lighter menstrual flow was “higher in the first dose compared to the second dose.”

However, the incidence of dysmenorrhea and heavier menstrual flow was “higher after the second dose compared to the first dose.”

The menstrual changes “occurred two to five times.”

The study authors conclude that “[t]here is an increased incidence of changes in menstrual cycle after COVID-19 vaccination, particularly in menstrual cycle length, menstrual pain, and the flow of menstruation.”

“[O]ur findings indicate that, even in the absence of a history of menstrual irregularities, there is an increased incidence of such irregularities following COVID-19 vaccination in Saudi women of childbearing age,” they write.

“The most frequently reported menstrual changes included alterations in the duration of the period, late periods, and dysmenorrhea. Further studies are recommended to investigate the impact of COVID-19 vaccines on women's health and explore the underlying physiological mechanisms.”

The study was conducted in Saudi Arabia, which administered mRNA vaccines BNT162b2 (Pfizer) and ChAdOx1 (Jenner Institute, University of Oxford).

The new findings corroborate an April 2022 study published in The Gazette of Medical Sciences that confirmed the “unprecedented rise” in dysmenorrhea that occurred in 2021 following the distribution of COVID-19 vaccines.

That study emphasized how decidual cast shedding (DCS)—also known as membranous dysmenorrhea; a gynecological event during which the mucus lining of the uterus is shed in one large piece—is historically a rare gynecological event.

Less than 40 DCS cases have been reported in the medical literature over the last 109 years.

However, 292 women reported having experienced DCS in 2021 alone, according to a survey distributed via social media from May 16 through December 31 of that year.

The study authors noted search terms for “decidual cast shedding” substantially increased during the months of April, May, and June 2021, according to Google metadata.

“These peaks in searches represented a 2000% increase over the first quarter of 2021,” the study authors write.

As a possible cause of this DCS phenomenon, the authors hypothesize that the COVID vaccine “interrupts the complex balance of ovulation orchestrated by the hypothalamic-pituitary-ovarian axis and thus produces anovulatory bleeding disorders.”

“It is known from COVID-19 mRNA vaccine documents that there is concentration of the nanolipid particles and the mRNA cargo in the ovaries,” they add. “This produces significant inflammatory response in the ovaries and could contribute to menstrual abnormalities, although there are many other potential mechanisms that could be involved.”