Impact of COVID-19 vaccine on menstrual cycle: A cross-sectional study

Background: According to recent reports, many women who received COVID-19 vaccine reported symptoms of menstrual irregularity. However, this finding is still unclear. Therefore, this study aimed to determine the prevalence of women with menstrual cycle changes following receiving COVID-19 vaccines and identify the risk factors associated with menstrual cycle changes during the pandemic. Material and methods: A cross-sectional descriptive study was conducted among women aged 20-40 years attending the outpatient clinics, general gynecology and reproductive and endocrine and infertility medicine department (REIMD) at King Fahad Medical City (KFMC) hospital in Riyadh, Saudi Arabia. Demographic data, medical and COVID-19 vaccination history, detailed menstrual cycle duration and frequency were obtained. Results: A total of 1117 women participated in this study. The age of 35.2% of them ranged between 24 and 29 years. Most (72.6%) of regular cycles before uptaking of COVID-19 vaccine became irregular. On the other hand, 17% of irregular cycles before uptaking the vaccine became regular, p<0.001. Vast majority of the participants (98.6%) had received COVID-19 vaccine. More than half of them (51.4%) had taken three doses. The most frequently reported vaccine was Pfizer-BioNTech (70.4% -83.5%). Frequency of menstrual cycles have increased from 29.64±16.29 days before uptaking of COVID-19 vaccine to 62.11±173.12 after uptaking it, p<0.001. In addition, rate of heavy bleeding increased from 12.4% before uptaking of the vaccine to 24.9%, p<0.001. Conclusion: Frequency and amount of menstrual bleeding were affected after intake of COVID-19 vaccine. However, number of doses and vaccine type were not associated with menstrual changes.