Research from the US states that vaccinated women Covid-19 experienced a delay in menstruation by about a day compared to those who were not vaccinated.
Although late, but according to research conducted on nearly 4,000 people and published in Jurnal Obstetrics & Gynecology expressing the number of days of menstruation will not be affected.
Lead author Alison Edelman of Oregon Health & Science University told AFP the effects were small and expected to be temporary, a finding that was “very convincing” and validated those who experienced the changes.
A menstrual cycle generally lasts about 28 days, but the exact amount varies from woman to woman, as well as within a person’s lifetime. It can also change during times of stress.
For their study, the scientists analyzed anonymous data from a fertility tracking app among women ages 18 to 45 who were not using hormonal contraception.
About 2,400 participants were vaccinated – the majority with Pfizer (55 percent), followed by Moderna (35 percent) and Johnson & Johnson (seven percent).
About 1,500 women who were not vaccinated were also included for comparison.
Immune response to vaccines
On average, the first dose of vaccine was associated with an increase in cycle length of 0.64 days and the second dose with an increase of 0.79 days, when comparing the vaccinated and unvaccinated groups.
The immune system’s response to the vaccine may be behind the changes.
“We know that the immune system and the reproductive system are intertwined,” says Edelman.
An increased immune system might impact the hypothalamic-pituitary-ovarian axis — what Edelman calls “the highway of how your brain talks to your ovaries, talks to your uterus,” or simply “the body clock.”
In particular, the production of inflammatory proteins called cytokines appears to interfere with the way this axis regulates the timing of the menstrual cycle.
The changes were most pronounced when vaccination was performed early in the follicular phase, which begins on the first day of the menstrual period (bleeding) and ends when ovulation begins.
(tst/chs)
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