This study aims to describe the phenomenology of obsessive-compulsive symptoms (OCS) and disorders (OCD) in perinatal women and to explore the relationship of OCS/OCD to postpartum depression. A prospective longitudinal study of 44 women screened with the Obsessive-Compulsive Inventory-Revised (OCI-R) and Edinburgh Postnatal Depression Scale (EPDS) between 30 and 37 weeks of pregnancy. Twenty-four women completed a diagnostic interview and the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) before delivery and were contacted postpartum to repeat the EPDS and Y-BOCS. In the third trimester, 32% reported high levels of anxiety and/or depressive symptoms (EPDS ≥ 10 and/or OCI-R ≥ 15) and 29% of those who completed the diagnostic interview met criteria for OCD. At 1 month postpartum, 12.5% had new OCS (Y-BOCS ≥ 8) and 25% had new high levels of depressive symptoms (EPDS ≥ 10). OCS increased in intensity postpartum but did not change in character. OCD and OCS may be of greater prevalence during the perinatal period than previously recognized. The high rates provide new information and require replication in larger, more diverse populations. Research in the perinatal period must expand beyond the exploration of depression to include anxiety disorders and specifically OCD.