Oregon Health and Science University analyzed data from about 4,000 women using the Natural Cycles fertility tracking app. Of these, 2.4 thousand received both doses of one of the mRNA vaccines (Pfizer or Moderna), another 1.5 thousand participants were not vaccinated. Scientists managed to obtain data on three consecutive cycles before vaccination and three more after vaccination, they were compared with information on six menstrual cycles in unvaccinated participants.
The researchers found that in vaccinated women, the interval between periods increased by an average of one day after the first component of the vaccine. At the same time, the duration of bleeding did not change. According to scientists, these fluctuations are within normal limits and are not a pathology. In addition, for most of the participants, the increase in the menstrual cycle was temporary.
“These results provide the first opportunity for women to understand what to expect from a COVID-19 vaccination so they can plan their lives accordingly,” the authors said. They noted that this study was one of the first of its kind, since the effect of various vaccines (and not only from coronavirus) on the menstrual cycle has not been studied before.
In the near future, scientists intend to focus on assessing the relationship of vaccination with other characteristics of menstruation: the intensity of bleeding, changes in mood, weight and pain.
The nonprofit health care system Northwestern Medicine previously discovered that the stress of the pandemic has a negative impact on the menstrual cycle in women. Most of the study participants reported changes in the duration of the menstrual cycle (50%), the duration of the period (34%), as well as various premenstrual symptoms that were not there before.
The most important finding was that longer menstrual periods and heavy bleeding were associated with the highest rates of stress and depression experienced. The more stressed and depressed a woman is, the more likely it is that it will affect her reproductive health, scientists say.