Association between COVID-19 and vaccination on menstrual cycle

Objective: To evaluate changes in the menstrual pattern of women of reproductive age infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or vaccinated against coronavirus disease 2019 (COVID-19). Methods: A cross-sectional study at the University of Campinas, Brazil using Google questionnaire applied from December 2021 through February 2022, disseminated through snowball technique. Participants responded about characteristics of their menstrual cycle before the pandemic and before COVID-19 vaccination, and then about characteristics of their cycle 3 months after infection with SARS-CoV-2 and 3 months after vaccination. Our primary outcome was a binary indicator of changes in the menstrual cycle. We used multivariate regression analysis to identify factors associated with menstrual changes. Results: We received 1012 completed questionnaires and 735 (72.7%) were from women aged between 20 and 39 years, 745 (73.6%) were White and 491 (48.6%) lived with a partner. A total of 419 (41.6%) of the women reported SARS-CoV-2 infection; however, only two of them were hospitalized, and 995 (98.8%) of women had at least one dose of COVID-19 vaccine. About menstrual characteristics, 170 (41.3%) reported changes after having COVID-19 and 294 (29.9%) after COVID-19 vaccination, respectively. Few years of schooling, lower income, and non-white ethnicity were related to higher reports of menstrual changes after COVID-19. Menstrual changes after COVID-19 vaccination were associated with not using contraception. Higher body mass index was associated with irregularities in cyclicity and bleeding days, after COVID-19 and COVID-19 vaccination, respectively. Conclusion: Our results corroborated the stability of the menstrual cycle after having COVID-19 or COVID-19 vaccination; however, there is a potential relationship between menstrual changes and socioeconomic factors as well as contraceptive use.