COVID-19 vaccination is associated with an average increase in menstrual cycle length of less than one day, a study published in the British Medical Journal has found. The researchers from Oregon Health & Science University, US, determined that on average, vaccinated people experienced an increase of less than one day in each menstrual cycle in which they were vaccinated. Changes in cycle length did not differ according to the type of vaccine received, the researchers noted. A change in cycle length of less than eight days is considered within the normal range of variation, they said. Although small menstrual changes may not be meaningful to health care professionals and researchers, the study authors noted that perceived changes in a bodily function linked to fertility may be alarming to those experiencing it and could contribute to vaccine hesitancy.

Changes in cycle length did not differ according to the type of vaccine received, the researchers noted.

A change in cycle length of less than eight days is considered within the normal range of variation, they said.

Although small menstrual changes may not be meaningful to health care professionals and researchers, the study authors noted that perceived changes in a bodily function linked to fertility may be alarming to those experiencing it and could contribute to vaccine hesitancy. Of the total, 1,342 participants experienced a change in cycle length of eight or more days, comprising 6.2 per cent of vaccinated individuals and 5 per cent of unvaccinated individuals. Women who were younger and who had a longer cycle length before vaccination were more likely to experience the increase. The researchers analysed de-identified data from the fertility tracking app, Natural Cycles. Users of the app provided it information on their temperature and their menstrual cycles.

Source: PTI