More than 35,000 UK women have reported disrupted periods after receiving the coronavirus jab and now a study shows that it can cause a small delay to periods. Doctors explain what this might mean

Any products in this article have been selected editorially however if you buy something we mention, we may earn commission

If you've had the Covid vaccine or more recently your booster, did you notice your period was heavier or more painful? Or perhaps it was delayed or irregular? If yes, you're not alone. Doctors and health practitioners are seeing more women who are experiencing post-vaccine period disruption. "I've seen women experiencing changes in menstruation after their Covid vaccine, varying from early periods, heavier flows and increased cramping," confirms Dr Janice Johnston, medical director of US healthcare plan Redirect Health .

But now a study in the journal Obstetrics and Gynaecology  of nearly 4,000 women in the US has confirmed a link between the vaccine and periods, something that had previously been largely anecdotal. It found a small delay (less than a day) in the start of periods after the vaccine, although no change to the cycle length after first or second doses of the US-approved vaccines (which exclude Oxford Astrazeneca).

Period delay was the only metric being measured here and may go some way to confirming what doctors and women had been reporting both anecdotally and to the government's Coronavirus Yellow Card reporting scheme, which logs adverse post-vaccine experiences. Currently, more than 35,500 women have reported menstrual disruption after receiving one of the three UK-approved brands of coronavirus vaccine, including heavier than usual periods, delayed periods and unexpected vaginal bleeding. However,  the government says this is small  compared to the number of vaccine doses given and the frequency of menstrual changes generally. "The menstrual changes reported are mostly transient in nature. There is no evidence to suggest that Covid-19 vaccines will affect fertility and your ability to have children ," it says.

That doesn't mean that period irregularities should be considered an afterthought as they so often are in research, says Dr Victoria Male, a reproductive specialist in the Department of Metabolism, Digestion and Reproduction at Imperial College London. Writing in the British Medical Journal , she says that any possible link should be investigated to reassure women and allow them to plan around possible delays in their periods.

"Although reported changes to the menstrual cycle after vaccination are short-lived, robust research into this possible adverse reaction remains critical to the overall success of the vaccination programme," she says. Being armed with the facts could allay vaccine hesitancy among young women, she says which is "largely driven by false claims that Covid-19 vaccines could harm their chances of future pregnancy. Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears... Clear and trusted information is particularly important for those who rely on being able to predict their menstrual cycles to either achieve or avoid pregnancy."

It's important to keep things in perspective, says Dr Janice. "I think that it's important to point out that there is no need to be afraid of being vaccinated. Everybody's body is different so some may react slightly different to the vaccine than others, but even then those effects are so small and so minimal that it definitely outweighs any consequence of not having the vaccine."

Sex toy brand Womanizer conducted its own survey into how the Covid vaccine affects our periods. The small survey asked 552 people who had received their vaccination (first or second) whether they'd seen changes in their periods; one in five confirmed that the vaccination had an effect on their menstrual cycle. In 31 per cent of these, the period was heavier than usual while 29 per cent said their period was more painful than usual. For about 22 per cent, their period was delayed by a few days. Some also reported spotting or a longer period.

Clotting is also being flagged. Fertility expert Emma Cannon shared that more people had been coming to her with menstrual issues via social media and in her London clinic. "Both post-vaccine and post-Covid I have seen a significantly increased number of women reporting menstrual irregularities, including spotting, missed periods and clotting in menstrual blood," she said.

Heavier periods post-vaccine are among the most commonly noted changes. Dr Kate Clancy, a professor of anthropology at the University of Illinois, took to Twitter to share her story: "I'm a week and a half out from dose one of Moderna, got my period maybe a day or so early and am gushing like I'm in my 20s again."

How does the vaccine affect our periods?

This is where it gets tricky. Post-vaccine period changes aren't listed as a possible side effect of the vaccine making it hard to pin down an answer.

"Does this have to do with the way the vax response is mounting a broader inflammatory response?" suggested Dr Kate Clancy, on Twitter back in June.

Dr Male's BMJ article sheds some light. She writes that menstrual changes have been reported after both types of Covid-19 vaccine (MRNA and adenovirus vectored) "suggesting that, if there is a connection, it is likely to be a result of the immune response to vaccination rather than a specific vaccine component."

She points out that human papillomavirus (HPV) vaccines, which are routinely administered, have also been associated with menstrual changes. "Indeed, the menstrual cycle can be affected by immune activation in response to various stimuli, including viral infection: in one study of menstruating women, around a quarter of those infected with SARS-CoV-2 [covid] experienced menstrual disruption."

With so many factors affecting our periods, it's hard to pin down an exact reason. Ms Tania Adib, consultant gynaecologist at The Medical Chambers Kensington told us: "We don’t know how the vaccines affect periods. We do know that people are having delayed, irregular or heavy and painful periods but we don’t know whether they are directly related to the vaccine or whether there are other things going on in their lives, indirectly caused by having had Covid that are affecting their hormones."

Emma Cannon suspects that living in a pandemic, with all the life events and stressed that brings, is a major factor. "Emotions such as fear, shock and grief, as well as a lack of activity can disturb our menstrual cycles," she said. Why? Because high levels of cortisol, which we produce when we're stressed, can change our menstrual cycle.

It could be easier to explain why we're having extra painful periods, though. "While there isn't enough data to support why some women may be experiencing early starts or heavier flows, the increased cramping can be explained by the already widely known possible post-vaccine effect of body aches and soreness combined with already existing period cramps, creating a perfect storm," says Dr Janice.

What to do if you notice period changes

"If you notice any temporary changes in menstruation after receiving the vaccine don't panic, things should be back to normal by your next menstrual cycle," says Dr Janice. "If the changes persist you may want to speak to your doctor or gynaecologist."

"There is absolutely no evidence of long-term adverse effects on menstrual bleeding that have been noted to date in any of the clinical trials from the vaccines. If this was a significant issue, it would have been found in the trials and would have been listed as a possible side effect," she adds.

To try to get your period back on track, integrative skin and hormone doctor  Terry Loong  advises upping the self-care around the time of your vaccine and afterwards. "Eat plenty of wholesome nutritious food to boost detoxification, antioxidants and immunity," she says. "Eat good healthy fats, good quality protein and fibre which is good for hormones. Avoid alcohol which slows down liver detoxification. Optimise sleep, manage stress and take care of your mental health. Track your cycle and be mindful of your exercise, work and personal commitments especially in your luteal phase (after ovulation) when it's better for reflecting, gently moving and protecting your energy."

MORE GLOSS: The Covid vaccine and fertility: what you need to know