Perinatal depression includes major and minor depression occurring in pregnancy and one year postpartum. Affecting one in seven women, it is one of the most common pregnancy complications; however, it is often under recognized and undertreated. A personal history of perinatal or non-perinatal depression significantly increases risk. Screening using a validated instrument is recommended in the context of systems to ensure effective diagnosis, treatment, and follow-up. Evidence-based treatment includes psychotherapy and pharmacotherapy. Selective serotonin reuptake inhibitors are well-studied in pregnancy, are associated with low overall absolute risk, and are differentially secreted into breast milk. If left untreated, perinatal depression is associated with significant short- and long-term negative maternal-child consequences including, among many others things, poor bonding. Of note, maternal suicide exceeds hemorrhage and hypertensive disorders as a cause of maternal mortality. It is critical to recognize that one in five women who screen positive for perinatal depression will have bipolar disorder and are at highest risk for postpartum psychosis, suicide, and infanticide, especially if prescribed unopposed anti-depressant monotherapy. Women who screen positive for having bipolar disorder should be referred for psychiatric evaluation. This review contains 6 figures, 13 tables and 54 references Keywords: Pregnancy, Postpartum, Perinatal, depression, Mood disorder, Baby blues, Bipolar disorder, Psychosis, Psychotherapy, Psychopharmacology