To estimate the incidence and identify risk factors of postpartum hemorrhage (PPH) after vaginal delivery.A systematic review and meta-analysis was conducted. PubMed, Cochrane Library, CINAHL, Web of Science, EMBASE, and ClinicalTrials.gov databases were systematically searched from inception to April 30th, 2022. Cross-sectional, cohort, case-control, and secondary analysis of randomized controlled studies that reported the incidence of PPH and the related risk factors in vaginal delivery were eligible through screening of 2343 articles. The incidence, associated standard error, adjusted odds ratios, relative risks and associated 95% confidence intervals were combined in the meta-analysis.Thirty-six articles were included in the descriptive review. The incidence of PPH (blood loss ≥500 mL and blood loss ≥1000 mL) was 17% and 6%, respectively. Forty-one identified risk factors were divided into five categories under two criteria: history and demographics; maternal comorbidity; pregnancy-related factors; labor-related factors; delivery-related factors.With the increasing incidence of PPH globally, obstetric health care providers need to improve their awareness of these multi-factorial risks to optimize obstetric care and reduce maternal morbidity. This systematic review and meta-analysis have raised important questions about the nature of vaginal delivery, such as the duration of prolonged labor, details on the use of oxytocin, and the presence of genital tract trauma. There should be highlighted by obstetric personnel on these factors during a patients' labor process.© 2023 Japan Society of Obstetrics and Gynecology.