<b>Background</b>Maternal anxiety negatively influences child outcomes. Reliable estimates have not been established because of varying published prevalence rates.<b>Aims</b>To establish summary estimates for the prevalence of maternal anxiety in the antenatal and postnatal periods.<b>Method</b>We searched multiple databases including MEDLINE, Embase, and PsycINFO to identify studies published up to January 2016 with data on the prevalence of antenatal or postnatal anxiety. Data were extracted from published reports and any missing information was requested from investigators. Estimates were pooled using random-effects meta-analyses.<b>Results</b>We reviewed 23 468 abstracts, retrieved 783 articles and included 102 studies incorporating 221 974 women from 34 countries. The prevalence for self-reported anxiety symptoms was 18.2% (95% CI 13.6-22.8) in the first trimester, 19.1% (95% CI 15.9-22.4) in the second trimester and 24.6% (95% CI 21.2-28.0) in the third trimester. The overall prevalence for a clinical diagnosis of any anxiety disorder was 15.2% (95% CI 9.0-21.4) and 4.1% (95% CI 1.9-6.2) for a generalised anxiety disorder. Postnatally, the prevalence for anxiety symptoms overall at 1-24 weeks was 15.0% (95% CI 13.7-16.4). The prevalence for any anxiety disorder over the same period was 9.9% (95% CI 6.1-13.8), and 5.7% (95% CI 2.3-9.2) for a generalised anxiety disorder. Rates were higher in low- to middle-income countries.<b>Conclusions</b>Results suggest perinatal anxiety is highly prevalent and merits clinical attention. Research is warranted to develop evidence-based interventions.