OBJECTIVE: The objective of this study is to determine the prevalence of placenta previa among different racial and ethnic groups. STUDY DESIGN: We conducted a retrospective cohort study to examine the prevalence of placenta previa among five major racial and ethnic groups: African American, Asian, Caucasian, Hispanic and Native American. We included all deliveries >/= 20 weeks gestation from a large northern Californian Health Maintenance Organization from 1995-2006. A multivariable logistic regression model was used to control for potential confounders. RESULT: Of the 394 083 deliveries in our cohort, 1580 (0.40%) were complicated by placenta previa. The prevalence of placenta previa was: Asian 0.64%, Native American 0.60%, African American 0.44%, Caucasian 0.36%, Hispanic 0.34% and unknown 0.31% (P<0.001). In our multivariable logistic regression model, only Asians (odds ratio (OR) 1.73, 95% confidence intervals (CI) 1.53-1.95) and African Americans (OR 1.43, 95% CI 1.19-1.72) were at increased risk for having placenta previa, compared with Caucasians. CONCLUSION: Asian women have the highest prevalence of placenta previa.