Affective illness is common in women, and the puerperium is a time of particular vulnerability. Gender differences in the expression of affective disorders have been attributed to the impact of hormonal influence, socialization, and genetics. Dramatic fluctuations in gonadal hormones that occur following childbirth, influences the increased incidence of mood disorders during this time. Numerous tools including the Edinburgh Postpartum Depression Scale can be used to screen for depression during pregnancy and postpartum. While screening tools may assist with appropriately identifying women who should be further assessed, their use alone does not significantly increase treatment seeking in women, even when their providers are notified about risk. Many studies demonstrate that only a small number (18%) of women who meet criteria for major depressive disorder seek treatment during pregnancy and postpartum. Additionally, common symptoms of depression (sleep, energy and appetite change) may be misinterpreted as normative experiences of pregnancy.Treatment engagement is important as untreated depression during pregnancy may have unfavorable outcomes for both women and children. Complications of pregnancy associated with depression include: inadequate weight gain,under utilization of prenatal care, increased substance use, and premature birth. Human studies demonstrate that perceived life-event stress, as well as depression and anxiety predicted lower birth weight, decreased Apgar scores, and smaller head circumference, and small for gestational age babies. Postpartum depression (PPD) is a common clinical disorder occurring in 15% of deliveries,making it one of the most frequent conditions to complicate pregnancy. Risk factors include past personal or family history of depression, sing marital status, poor health functioning, lower SES, and alcohol use. Women who have a prior history of postpartum depression, particularly with features of bipolarity or psychosis may be at particularly high risk.