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Introduction: Menstrual disorders are commonly reported after COVID-19 vaccination and heavy menstrual bleeding was added to the product information of the COVID-19 vaccines of Moderna and Pfizer. The aim of this review, using a systematic search, is to provide an overview of available literature on the risk of menstrual disorders after COVID-19 vaccination. Methods: The review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. A PubMed search was performed on 15 August 2023, including solely quantitative studies in English and Dutch. Results: A total of 61 studies were included, of which 40 were cross-sectional studies, 18 cohort studies, and three self-controlled case series. Outcomes included a wide variety of menstrual disorders, including changes in cycle length (n = 54), changes in the amount of bleeding (n = 44), changes in menses length (n = 30), changes in the experience of (pre)menstrual pain (n = 21), and breakthrough bleeding (n = 18). All included studies found a higher percentage of at least one menstrual disorder in the first cycle after different types of COVID-19 vaccination and after different doses. Discussion: In conclusion, evidence suggests that COVID-19 vaccines may cause menstrual changes in women of reproductive age. However, there is a need for more longitudinal studies because of important limitations in the study designs of many of the included studies. Although menstrual changes are short-lived and predominantly mild, it is important for women and healthcare professionals to be informed about these potential adverse reactions and to assess these events in clinical trials on vaccines. [ABSTRACT FROM AUTHOR]

Aims: During the COVID‐19 vaccination campaigns, the number of reports of menstrual abnormalities increased rapidly. Here, we describe the nature and potential risk factors associated with menstrual abnormalities based on spontaneously reporting data as well as data from a prospective cohort event monitoring (CEM) study as these are poorly studied. Methods: Reports of menstrual abnormalities received by the Netherlands Pharmacovigilance Centre Lareb in the spontaneous reporting system between February 2021 and April 2022 were summarized. In addition, logistic regression analysis was performed on the reported menstrual abnormalities in the CEM study to assess the association between person characteristics, prior SARS‐CoV‐2 infection and use of hormonal contraceptives and the occurrence of menstrual abnormalities after vaccination. Results: We analysed over 24 000 spontaneous reports of menstrual abnormalities and over 500 episodes (among 16 929 included women) of menstrual abnormalities in the CEM study. The CEM study showed an incidence of 41.4 per 1000 women aged ≤54 years. Amenorrhoea/oligomenorrhoea and heavy menstrual bleeding collectively accounted for about half of all abnormalities reported. Significant associations were observed for the age group 25–34 years (odds ratio 2.18; 95% confidence interval 1.45–3.41) and the Pfizer vaccine (odds ratio 3.04; 95% confidence interval 2.36–3.93). No association was observed for body mass index and presence of most comorbidities assessed. Conclusion: The cohort study showed a high incidence of menstrual disorders among women aged ≤54 years, and this observation was supported by the analysis of spontaneous reports. This suggests that a relation between COVID‐19 vaccination and menstrual abnormalities is plausible and should be further investigated. [ABSTRACT FROM AUTHOR]