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5 Things to Know about the COVID-19 Vaccine and your Menstrual Cycle

By Dr. Kristina Adams Waldorf, Sara Rutz, Isabelle Crary and Carly Baxter

Minimal impact of the COVID-19 vaccine on menstrual period cycles
Some individuals have voiced concerns about the effects of the COVID-19 vaccine on menstruation. In response to this concern, a large study was conducted over the span of several months, tracking the menstrual cycles of nearly 4,000 vaccinated and unvaccinated individuals. Results show that there was minimal change in cycle length. The first dose of the COVID-19 vaccination (Pfizer, Moderna, or J&J) was associated with a longer cycle length by 0 .7 days , and the second dose was associated with a 0.9 day increase. For those that received both doses of a vaccine in the same cycle, the study found that the average cycle was prolonged by about 2 days. Many individuals are unlikely to notice these small changes, however, this information may be valuable for those that track their cycles closely. While the menstrual cycle was found to be transiently prolonged following vaccination, there was no change to the length of menses. This means that following vaccination, there may be a slightly extended time between periods, however, period length should remain the same. 

The COVID-19 vaccine (and related menstrual changes) do not affect your ability to get pregnant
Many individuals are understandably concerned that any change or irregularity to their menstrual cycles as a result of the COVID-19 vaccine may affect their fertility. However, studies have shown that there is no correlation between the COVID-19 vaccine and fertility. In fact, getting the COVID-19 vaccine can help protect you and your baby from serious complications from COVID-19. 

Having COVID-19 could disrupt your cycle
In a study of 127 women with the COVID-19 disease, 16% noticed changes in their menstrual cycle, which most commonly was reported as an irregular period. Interestingly, women reporting more COVID-19 symptoms were more likely to have an abnormal period. In summary, it appears that irregular periods are commonly reported after COVID-19 disease (16%), especially when women are ill, and rarely after COVID-19 vaccination (<1%). More research still needs to be done on this topic. 

The stress of the pandemic itself may cause period changes
A normal period can vary widely from person to person and month to month. Exercise, diet and even stress can change a period, as well as many medications including birth control. Several studies in different countries indicate that the psychological stress of the pandemic has increased the irregularity of women’s periods. Talk to your OB/GYN or primary care doctor if you are concerned about menstrual changes Changes to your menstrual cycles, both in terms of the length of the cycle, amount of bleeding, and premenstrual symptoms is normal. However, it can be stressful knowing which changes are worrisome and which are normal, especially if you are trying to get pregnant or have concerns about fertility. OB/GYNs and primary care doctors are excellent resources who can guide and support you through understanding these changes in your body. Your physicians can counsel you on how COVID-19 and the COVID vaccine does and does not affect your body. Prioritizing your mental and physical health during a stressful time can play a key role in supporting fertility, pregnancy, and caring for young children. 

What does this all mean?
The COVID-19 vaccine was found to be associated with a brief, minor increase in cycle length, however, there were no significant effects on the length of menses. This means that you may notice an extra day or two between periods, but this should resolve after a few cycles. Data indicates that the vaccine does not negatively affect ovulation, fertility or pregnancy. The vaccine is highly recommended and is the best way to protect you against hospitalization and severe disease with COVID-19.

Meet the Authors

Kristina Adams Waldorf, MD

Kristina Adams Waldorf, MD is a Professor of Obstetrics and Gynecology and Adjunct Professor of Global Health at the University of Washington School of Medicine. She is an internationally recognized expert in how infections impact pregnancy and how vaccines and therapeutics protect the mother and fetus. She is Chair of the National Institutes of Health Obstetrics and Maternal-Fetal Biology Study Section. She is a member of the Center for Reproductive Sciences and the Center for Innate Immunity and Immune Diseases. Her grant support has come from the National Institutes of Health, the March of Dimes, Burroughs-Wellcome Fund, the Canadian Institute for Health Research and the Australian National Medical Research Council.

Sara Rutz

Sara Rutz graduated from the University of Alaska, Anchorage with a Bachelor of Science degree in Natural Sciences and a minor in Psychology. She is now a fourth year medical student at the University of Washington School of Medicine. Prior to medical school, she worked with diverse & underserved populations in patient care settings and as an insurance specialist for 5 years. She has been involved in research on improving outcomes for infants with Neonatal Opioid Withdrawal Syndrome, quality improvement in obstetric care, and providing up to date information as a volunteer for the COVID-19 Literature Surveillance Team. She is passionate about reproductive medicine and improving access to care for rural and underserved populations.

Carly Baxter

Carly Baxter graduated from the University of Puget Sound with a Bachelor of Science degree in Biology and a minor in French studies. She is now a third year medical student at the University of Washington School of Medicine. She has worked with the MaMHA (Maternal Mental Health Access) group coordinated by the University of Washington and WA Department of Health in an effort to reduce maternal mortality rates in WA state. She is passionate about reproductive justice, equitable health care access and volunteering within her community at local health fairs.

Isabelle Crary

Isabelle Crary graduated from Stanford University with a Bachelors of Arts in Human Biology. She is now a third year medical student at the University of Washington. She has been involved in research on anemia in pregnancy, breast cancer prevention and treatment, and adolescent nutrition. She is passionate about healthcare for individuals who are pregnant, reproductive justice and nutrition education.