This study aimed to identify subgroups of pregnant women at imminent (1 year) risk for major depressive episodes. Participants were 84 low-income, predominantly Mexican women using public sector obstetrics services who participated in monthly interviews during pregnancy and up to 6 months postpartum. Participants were designated a priori as "more vulnerable" or "less vulnerable" to future perinatal depression based on evidence of mood regulation problems defined as (a) a self-reported history of major depressive episodes, (MDE) and/or (b) high current depressive symptom scores on a continuous depression scale. Two definitions of a major depressive episode based on meeting 2 or 3 DSM-IV MDE criteria, were used to measure the incidence of a new major depressive episode. Results suggest that more vulnerable groups (i.e., with the greatest mood regulation problems) had a higher incidence of major depressive episodes than less vulnerable groups. Implications for screening and developing preventive interventions for postpartum depression are discussed.