Background: COVID-19 vaccines have provided fertile ground for research, especially with the unprecedented spread of misinformation about this disease and its vaccines. Among women, one of the most frequently reported side effects of the vaccine has been menstrual disturbance.

Objective: To investigate the perceived impact of COVID-19 vaccines on the menstrual cycle. In addition, the research seeks to identify factors that could predispose certain individuals to experience these effects, thereby contributing to a deeper understanding of the interplay between vaccines and menstrual health.

Design: We conducted a retrospective observational cross-sectional study.

Methods: Any woman of menstruating age who received at least one dose of the COVID-19 vaccine and currently resides in Saudi Arabia was invited to complete an online questionnaire. The questionnaire compared menstruation characteristics-regularity, volume, intermenstrual bleeding, and dysmenorrhea-before and after receiving the COVID-19 vaccine, taking into consideration possible predisposing factors such as polycystic ovarian syndrome, contraceptives, or period-blocking pills.

Results: Women without polycystic ovarian syndrome experienced less change in dysmenorrhea post-vaccine compared to those with polycystic ovarian syndrome (23.88% versus 37.78%, p = 0.045). Women using hormonal contraceptives were about two times more likely to experience changes in volume compared to those not using contraceptives (odds ratio = 2.09, 95% confidence interval = 1.23-3.57, p = 0.006). COVID-19 vaccine skeptics were about three times more likely to perceive changes in regularity post-vaccine compared to non-skeptics (odds ratio = 2.96, 95% confidence interval = 1.79-4.90, p < 0.001). They were also three times more likely to perceive changes in volume post-vaccine (odds ratio = 3.04, 95% confidence interval = 1.95-4.74, p < 0.001).

Conclusion: Our data suggest significant associations between COVID-19 skepticism, the use of hormonal contraceptives, and the reported post-vaccine menstrual disturbances. This underscores the importance of public education efforts aimed at dispelling misinformation and addressing controversies related to these vaccines.