Adverse Menstrual Events Reported After and Before (or Without) COVID-19 Vaccination: A Systematic Review and Meta-Analysis of Comparative Observational Studies.

ABSTRACT

BACKGROUND: Reports of adverse menstrual events emerged during the COVID-19 vaccination campaign in multiple countries. This raised the question whether these reports were caused by the vaccines. The aim of this systematic review was to evaluate comparative studies on this topic (registered at PROSPERO [CRD42022324973]). METHODS: We included observational studies such as cohort studies and surveys comparing the response to self-reported questionnaires between post- versus pre-vaccination data. PubMed and Cochrane Library searches were conducted on 1 September 2023. The primary outcome was the incidence of any prespecified adverse menstrual event, and the outcome measure was the risk ratio. The meta-analysis was conducted by using the Mantel-Haenszel method and the random effects model. We summarized the results on risk factors as well as key findings of the studies included. RESULTS: We retrieved 161 references from electronic databases and additional sources such as references lists. Of those, we considered 21 comparative observational studies. The meta-analysis of any adverse menstrual adverse event reported in 12 studies resulted in a pooled estimate (risk ratio 1.13; 95% CI, 0.96-1.31) that did not favor any group. The analysis was constrained by considerable clinical and statistical heterogeneity. Risk factors for self-reported menstrual changes included a history of COVID-19 infection, the concern about COVID-19 vaccines, smoking, previous cycle irregularities, depression, and stress, and other issues. CONCLUSIONS: The risk ratio did not favor any group and heterogeneity was prevalent among the studies. Most studies suggested that the reported changes were temporary, minor, and nonserious.