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RCOG/FSRH respond to reports of 30,000 women’s periods affected after COVID-19 vaccine

16 Sept 2021

The RCOG and FSRH are aware that over 30,000 people have reported to the MHRA Yellow Card scheme that they have had changes to their menstrual cycle after having the COVID-19 vaccine.

In this BMJ article, Dr Viki Male, lecturer in reproductive immunology, says most of these changes are temporary and periods return to normal after a single cycle.

This BBC article highlights the issue, and calls for more research.


Responding to this, Dr Jo Mountfield, Vice President of the Royal College of Obstetricians and Gynaecologists, said:

“We understand that any changes to periods following a COVID-19 vaccine can be concerning. We want to reassure women that any changes generally revert back to normal after one or two cycles. We would encourage anyone who experiences heavy bleeding that is unusual for them, especially after the menopause, to speak to a healthcare professional.

“There is no evidence to suggest that these temporary changes will have any impact on a person’s future fertility, or their ability to have children. It is important to get vaccinated as the best protection against coronavirus. This is especially important if you are planning a pregnancy, as we know unvaccinated pregnant women are more at risk of becoming seriously ill from COVID-19.

“We support calls for more research to understand why women may be experiencing changes to their menstrual cycle after having the vaccine.”


Dr. Sarah Hardman, Specialty Doctor SRH, Menopause Lead Chalmers Centre, and Co-Director of the FSRH Clinical Effectiveness Unit, said:

"There isn't evidence to indicate that fertility is affected by either Covid-19 infection or Covid-19 vaccination.

“There have indeed been reports of disturbance in menstrual bleeding pattern around the time of both Covid-19 vaccination and Covid-19 infection. Some reports relate to individuals using hormonal contraception and some relate to individuals having natural menstrual cycles. Most cases appear to resolve spontaneously and rapidly, which is generally reassuring for subsequent fertility. There is no indication that effectiveness of hormonal contraception is affected.

“The available evidence does not confirm or exclude either Covid-19 infection or Covid-19 vaccination as causes of change in bleeding pattern. Menstrual disturbance is common and cases may well have occurred coincidentally around the time of Covid-19 illness or vaccination. There isn't a clear indication of how the infection or vaccination would cause the change. The fact that there are many reports of altered bleeding pattern may simply reflect normal variation in bleed pattern amongst the millions of individuals that have had Covid-19 infections and Covid-19 vaccination."


Dr Jackie Maybin, Senior Clinical Research Fellow and Consultant Gynaecologist, MRC Centre for Reproductive Health, University of Edinburgh said:

“There have been lots of anecdotal reports of people with menstrual disturbance following COVID-19 vaccination, including changes in frequency, duration, regularity and volume of menstruation. It is very difficult to know if these changes are a direct effect of the vaccine itself or are due to wider effects of the pandemic. Menstrual disturbance has also been reported in those experiencing acute COVID-19 and Long COVID.

“At this stage, it is difficult to be certain regarding the mechanisms causing these effects. It may differ from person to person. The brain, ovaries and womb interact to control the menstrual cycle. Menstrual disturbance may be due to effects on the part of the brain that controls the reproductive hormones, effects on the ovaries or effects directly on the lining of the womb (which is what is shed during a period). 

“In times of stress, the female system is designed to temporarily downregulate to prevent against pregnancy and conserve energy. This brain-level effect may explain some of the changes in menstruation observed during the pandemic, with COVID-19 or with vaccination. The COVID-19 vaccination itself is designed to initiate an immune response in the body to protect against future COVID-19 infection. The resulting inflammation may transiently affect the ovaries, altering their hormone production over one or two cycles, resulting in irregular or heavier menstrual bleeding. The inflammation may also temporarily alter how the womb lining breaks down and sheds, causing a heavier period. These effects could lead to temporary changes in menstrual symptoms that should spontaneously resolve.

“It is important to emphasise that any effects of the vaccine are likely to be short lived and much less severe than those associated with COVID-19 infection. Women who are called for the vaccine shouldn't be deterred from attending.”



To contact the RCOG press office call +44 (0) 7986 183167 or email .

About FSRH

The Faculty of Sexual and Reproductive Healthcare (FSRH) is the largest UK multi-disciplinary professional membership organisation working at the heart of sexual and reproductive health (SRH), supporting healthcare professionals to deliver high quality care. It works with its 15,000 members, to shape sexual reproductive health for all. It produces evidence-based clinical guidance, standards, training, qualifications and research into SRH. It also delivers conferences and publishes the journal BMJ Sexual & Reproductive Health in partnership with the BMJ. For more information please visit:

About RCOG

The Royal College of Obstetricians and Gynaecologists (RCOG) is a medical charity that champions the provision of high quality women’s healthcare in the UK and beyond. It is dedicated to encouraging the study and advancing the science and practice of obstetrics and gynaecology. It does this through postgraduate medical education and training and the publication of clinical guidelines and reports on aspects of the specialty and service provision. For more information, visit:

  • Clinical and research
  • Pregnancy and birth