Some people experience headaches or sore
arms after getting vaccinated. Others may have nausea or swollen lymph nodes.
Now, a growing body of research is pointing to yet another potential side
effect of COVID-19 vaccines: changes in
menstrual cycles.
اضافة اعلان
In a study
published last Tuesday in BMJ Medicine, researchers reported that, on average,
vaccinated people experienced about a one-day delay in their periods compared
with those who did not get vaccinated. But like other side effects of vaccines,
this change was temporary. One cycle after vaccination, cycles tended to return
to normal.
The research expands on the team’s earlier findings
as well as anecdotal reports from people who noticed erratic periods after
receiving their shots. It includes data from nearly 20,000 people around the
world — 14,936 of whom were vaccinated and 4,686 who were not.
“Menstruation is woefully understudied, which is
troubling considering it is a key indicator of fertility and overall health,”
said Dr Alison Edelman, a professor of obstetrics and gynecology at Oregon
Health & Science
University School of Medicine and the paper’s lead author.
“We hope our findings further validate what so many
individuals reported experiencing and allow health care professionals to
provide patients with better care and clinical recommendations.”
It is normal to experience some level of variation
in your menstrual cycle. The hormones that regulate your monthly cycle can be
affected by a variety of factors, including stress, weight loss or weight gain,
calorie restriction, and intense exercise. As a result, the number of days you
bleed, the length of your cycle, and the heaviness of your flow can fluctuate.
According to the International Federation of
Gynecology and Obstetrics, changes in cycle length that are less than eight
days are within a normal range.
When Edelman and her team analyzed study
participants’ data from three consecutive menstrual cycles before vaccination
and at least one cycle after, the researchers found that the cycles increased
by 0.71 days after the first dose and by 0.56 days after the second dose.
Individuals who received both shots during the same menstrual cycle experienced
a bigger change: Their periods were, on average, almost four days late. In this
subgroup, 100 people noticed a delay of eight days or more.
Because menstrual cycles returned to baseline one
month after vaccination, these changes are unlikely to impact current or future
fertility, said Dr Jennifer Kawwass, a reproductive endocrinologist at Emory
University, who was not involved in the study.
It’s not yet clear exactly how the COVID vaccine
prompts these changes. There is most likely some crosstalk between the immune
system and other parts of the body that help protect against outside pathogens,
including the reproductive system. When vaccines activate your immune system,
it is possible that they also affect the endometrium, which lines the uterus
and is shed during menstruation.
The new paper
suggests that a variety of COVID vaccines may have this effect. Because it
included participants from around the world, researchers were able to study the
effects of not only the messenger RNA vaccines approved in the US (Pfizer and
Moderna), but also vaccines made from more traditional methods, like those
using engineered viruses (AstraZeneca, Covishield, Johnson & Johnson, and
Sputnik V) and inactivated viruses (Covaxin, Sinopharm, and Sinovac).
The study did not include data from people who were
on birth control or people who already had irregular cycles before getting
vaccinated.
Researchers cannot yet say whether you should time
your vaccine or booster shot to a certain point in your period, but the results
may help people plan ahead, as well as allay fears around missed periods for
people who experience a change in menstruation after getting vaccinated. The
fact that menstrual cycles quickly returned to normal also might help settle
concerns around newer mRNA vaccine technology.
Experiencing any side effect after getting
vaccinated — whether a change in menstruation or a headache or fever — is not
an indication of how well your vaccine is working. Some people are simply more
sensitive to immune-system or hormonal changes in the body, Kawwass said.
Infections of any kind can also disrupt
menstruation. Getting COVID has the potential to have more long-lasting and
serious effects than a fluctuation in your period.
Still, you may want to keep an eye out for any new
or unusual patterns of bleeding. “If an individual were to notice significant
changes in menstrual-cycle interval that continue for several months, it would
be reasonable to seek care from an obstetrician gynecologist for further
evaluation,” Kawwass said. “Such changes are unlikely to be the result of
vaccination.”
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