The average prevalence rate of non-psychotic postpartum depression based on the results of a large number of studies is 13%. Prevalence estimates are affected by the nature of the assessment method (larger estimates in studies using self-report measures) and by the length of the postpartum period under evaluation (longer periods predict high prevalences). A meta-analysis was undertaken to determine the sizes of the effects of a number of putative risk factors, measured during pregnancy, for postpartum depression. The strongest predictors of postpartum depression were past history of psychopathology and psychological disturbance during pregnancy, poor marital relationship and low social support, and stressful life events. Finally, indicators of low social status showed a small but significant predictive relation to postpartum depression. In sum, these findings generally mirror the conclusions from earlier qualitative reviews of postpartum depression risk factors.