Severe Post-COVID-19 Vaccine Menstrual Cycle Changes Are Underinvestigated

After swift acts by Congress, the Biden administration officially ended the COVID emergency on April 10, 2023. The Food and Drug Administration “amended the emergency use authorization of the Pfizer-BioNTech COVID-19, Bivalent vaccine on April 18th”. The original monovalent Pfizer-BioNTech COVID-19 vaccine is no longer available in America, as it is no longer authorized. The bivalent vaccine will now be used. Despite these changes, many people are questioning the effects of the original COVID-19 vaccines, including women whose menstrual cycles were disturbed. 

According to a large study published on July 15, 2022, many women experienced unexpected changes to their menstrual cycles post-COVID-19 vaccination. In the population studied, 42% of women with a normal menstrual cycle experienced heavy bleeding after being vaccinated. 44% of women with a normal menstrual cycle saw no change. Many women who did not have a regular menstrual cycle before vaccination saw breakthrough bleeding including 71% of women on long-acting reversible contraceptives, 39% of biological women on gender-affirming (cross-sex) hormones, and 66% of post-menopausal women.

A newer study published by the NIH on September 27, 2022, confirmed that there is a link between COVID-19 vaccination and a temporary increase in menstrual cycle length. The study confirmed an increase in women’s menstrual cycles by 0.71 days for one dose of a COVID-19 vaccine and 0.56 days for a second dose. These changes are more likely for young women who had long menstrual cycles before getting vaccinated.

These findings show that many women experience changes to their menstrual cycles post-COVID-19 vaccination. For the majority of women, it seems like the changes to their menstrual cycles are benign. However, some women experience more concerning and severe changes to their menstrual cycles after being vaccinated. A lack of research into more severe menstrual cycle changes after COVID-19 vaccination has left some women without answers. 

In October 2022, I spoke to one woman who experienced a severe symptom related to her menstrual cycle after getting vaccinated and boosted with the Pfizer vaccine. Felicity*, a woman in her 30s, finished her first COVID-19 vaccine series in August 2021 and received a booster in December 2021. In April 2022 she experienced an unexpected and terrifying phenomenon that left her fearful over a year later. 

Felicity has polycystic ovarian syndrome, so an abnormal menstrual cycle is nothing new to her. In January 2020, she took a Provera pill to induce her period. It worked, and she experienced spotting on and off for eighteen months after that. In April 2022, she took another Provera pill to induce her period, and she expected the pill to work the same way it had the time before. Instead of a normal period, Felicity began bleeding from her rectum and urethra as well as her vagina. A few days into the bleeding she began passing golf ball-sized vaginal blood clots and smaller blood clots from her rectum and urethra. Within two hours, Felicity passed what she described as “fifteen massive clots.” By the time she made it to A&E and a gynecologist, the blood clots had ceased but heavy bleeding continued.

A tranexamic acid prescription was able to stem Felicity’s heavy blood flow over the course of a week. Felicity assumes this extreme and abnormal period happened either because she was vaccinated or because she contracted COVID-19 in March. Unfortunately, doctors have not been able to find a cause for Felicity’s abnormal period, and some doctors have even been dismissive about her concerns. After multiple meetings with her general practitioner, Felicity has been told that she “must have imagined it” or “just had a UTI” or “just had hemorrhoids.” Some gynecologists have told her that she “must have forgotten what periods are like.” Felicity claims that she knows what her periods are supposed to be like and that this one was categorically different. She also claims that several other post-vaccination health issues have accompanied this abnormal period. 

Felicity said she does not “dare take Provera again”, and she is unsure of what other options are out there for her. She knows that having a period is a necessity, but she doesn’t know what to do or which medical professional to turn to. She is afraid that if she takes another pill to induce her period, she will have a similar experience and pass blood clots again, or have an even worse outcome. 

An uptick in the number of women shedding decidual casts after being vaccinated against COVID-19 is another reason Felicity feels uneasy. A small study from the Gazette of Medical Sciences published in April 2022 showed that 4.83% of 292 vaccinated women surveyed experienced the shedding of a decidual cast (the shedding of the entire uterine lining all at once). According to the study, Google searches for “decidual cast” and “decidual cast covid vaccine” increased by heavily in April, May, and June of 2021. 

In March 2023, I briefly communicated with Dr. Kimberly Biss, an obstetrician-gynecologist in the Tampa Bay and St. Petersburg, Florida region. She pointed me to Tiffany Perotto’s work at My Cycle Story, an independent study with peer-reviewed data about the severe menstrual cycle changes women have experienced since the COVID-19 pandemic. One of the main focuses of the articles on this site is about decidual cast shedding.

According to research from the GreenMedInfo Research Group (2022), fewer than 40 cases of decidual cast shedding were reported over a 100-year timeframe. In just 7.5 months during 2021, 292 women reported experiencing a decidual cast on a My Cycle Story survey. The 91-question survey was distributed to over 6,000 women aged 18 and older who were experiencing abnormal menstrual changes. 96.2% of the women in this group also reported having had health problems or menstrual irregularities since January 2021. The COVID-19 vaccines were rolled out in the US during this same month, leading researchers to suggest that the vaccines may be to blame. 

Unfortunately, the study from My Cycle Story can not determine exactly why there has been an increase in decidual cast shedding. Medical professionals have speculated that the reported decidual casts are not actually decidual casts at all, but “fibrin-laden clots” caused by the COVID-19 vaccine. The COVID-19 vaccine is associated with thromboembolism, or blood clots in the veins. 

Experiences like Felicity’s are being insufficiently investigated, underrepresented, and, in some cases, outright ignored. It is important for medical researchers to study these phenomena so we can better understand the potential risks of COVID-19 and COVID-19 vaccines. For women who have already experienced changes and abnormal menstrual symptoms, it is important to research solutions. As data begins to raise questions about the side effects of COVID-19 vaccines, we must also ask why certain institutions, specifically colleges, keep their vaccine mandates in place.