Do Covid-19 Vaccinations Increase the Length of the Menstrual Cycle?. Latest Updates!

Professor Alison Edelman discusses her recent research on the impact of COVID-19 immunizations on the menstrual cycle. Dr. Alison Edelman is an Obstetrics and Gynecology  professor at Oregon Health & Science University. I am a clinician-researcher at an academic hospital and medical school.

Public concern about COVID vaccinations and menstrual health led to our study, as did our desire to provide high-quality evidence to assist address a critical topic. Women’s menstrual cycles vary from month to month. So what?

True, menstrual cycles change from month to month and with time. Given the complexity of the human body, our bodies are not excellent timekeepers. Small fluctuations in menstrual cycle duration are frequent and should not be cause for alarm. Stress, contraception, changes in diet or exercise, age, medical issues, etc. can all affect the length of a person’s cycle. However, if a person notices changes over three months or a change in cycle duration of more than eight days, they should visit their doctor.

Despite millions of COVID-19 immunizations globally, little study has been done on the impact of vaccinations on the menstrual cycle. Why is it vital to look at all possible adverse effects?
Menstrual health has been understudied and undervalued in scientific study, particularly in vaccine trials. Contrary to popular belief, menstruation is regarded a ‘vital sign’ or an overt sign of health, well-being, and future fertility. I believe future research and vaccine trials should address this key sex and gender issue.

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Do Covid-19 Vaccinations Increase the Length of the Menstrual Cycle

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Our research looked at over 4,000 Americans who use the FDA-approved birth control app Natural Cycles. The study received de-identified data from all participants.

We used data from women who had clinically normal menstrual periods at baseline (pre-vaccine or if unvaccinated, had cycles over a similar time). No vaccination or Pfizer, Moderna or Johnson & Johnson COVID-19 vaccine.

The study indicated that women who menstruate may suffer a minor but transitory alteration in menstrual cycle duration after receiving a COVID-19 vaccination.

When a shot is given, the average difference in length is less than one day. Two vaccination doses in one menstrual cycle may cause a two-day difference.

The interval between a person’s first day of menses and their next first day of menses may be significantly longer than “average”. When a person gets the vaccine, their ‘period’ (menses) may start a day later than usual.

Notably, we found no differences in menstrual length ( bleeding period). The cycle length differences appear to disappear fast — as soon as the vaccination is not given the next cycle.

Why are your findings comforting to women? How can this study help educate women about the COVID-19 vaccine?
While the overall changes in menstrual cycle length do not meet professional societies’ definition of ‘clinical significance’ (8 days or more), any noticeable change in a person’s cycle – whether related to vaccination or other environmental stressors – can feel significant, especially if unexpected.

The study’s findings may be reassuring to women who reported menstruation irregularity after vaccination. As a professional, I now know what to expect and can prepare patients for this potential so they don’t have to worry.

If menstrual disruption is the only reason not to get vaccinated against COVID-19, this research should reassure that any alterations are minor, transient, and do not appear to have long-term health or reproductive effects.

Natural Cycles users are not necessarily representative of the general population. This demographic is more educated, white, and has a lower BMI than the national average. The inclusion criteria for our dataset may have offset the influence of BMI on menstrual cycle variability (needing 3 cycles pre-vaccine that met the criteria for normal cycle length).

We also know that additional research is needed on menstruation and immunizations. To maintain the statistical integrity of large population studies like this one, we must limit the number of questions we ask at a time. We’re working on the next series of questions to acquire more replies.

Prof. Alison Edelman
Dr. Alison Edelman directs the OHSU Complex Family Planning Section and Fellowship. She leads the Cochrane Fertility Regulation Group at OHSU. She is a lifer at OHSU, having completed her medical training and a family planning fellowship there (2003). While on fellowship, she earned an MPH from UW, Seattle (2003). Alison Edelman

Dr. Edelman is a funded clinician-scientist. She also works as a global technical consultant, adjusting global evidence to local context and resource availability, developing and implementing government guidelines, and creating and conducting research.

In addition, she is the Principal Investigator of OHSU’s NIH/NICHD-funded Contraceptive Clinical Trials Network site, Associate Editor of the journal Contraception, member of the expert working group for the Centers for Disease Control Medical Eligibility Criteria (MEC) for Contraceptive Use, and member of the World Health Organization’s Global Guidance for Contraceptive Use.

She presently chairs the ACOG’s Committee on Gynecology Practice Bulletins and is a member of the ACOG’s COVID-19 Gynecology Guidance group. Dr. Edelman specializes in family planning at the Center for Women’s Health.

Dr. Edelman’s research aims to fill important research gaps in family planning to improve the contraceptive experience for women and users. Suggesting innovative contraceptive options, increasing pain control using office-based gynecologic treatments, and doing and supporting Cochrane systematic reviews are among her research interests.

Her research has earned her the 2017 Charlotte Ellertson Innovation Award from the American Society for Emergency Contraception and the 2019 Daniel R. Mishell, Jr MD Outstanding Article Award.

On the NIH/NICHD Contraceptive Clinical Trials Network. NICHD uses OHSU and 12 other facilities across the country to create protocols and conduct clinical trials to help discover novel contraceptive techniques that are safe and effective.

Another goal is to improve emergency contraception. Higher BMI women are more likely than lower BMI women to have emergency contraception fail. We are monitoring women’s medication levels and ovarian function to figure out why this is happening.

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