Depression is often undiagnosed and untreated. It is not clear if differences exist in the diagnosis and treatment of depression among pregnant and nonpregnant women. We sought to estimate the prevalence of undiagnosed depression, treatment by modality, and treatment barriers by pregnancy status among U.S. reproductive-aged women.We identified 375 pregnant and 8,657 nonpregnant women 18-44 years of age who met criteria for past-year major depressive episode (MDE) from 2005-2009 nationally representative data. Chi-square statistics and adjusted prevalence ratios (aPR) were calculated.MDE in pregnant women (65.9%) went undiagnosed more often than in nonpregnant women (58.6%) (aPR 1.1, 95% confidence interval [CI] 1.0-1.3). Half of depressed pregnant (49.6%) and nonpregnant (53.7%) women received treatment (aPR 1.0, 95% CI 0.90-1.1), with prescription medication the most common form for both pregnant (39.6%) and nonpregnant (47.4%) women. Treatment barriers did not differ by pregnancy status and were cost (54.8%), opposition to treatment (41.7%), and stigma (26.3%).Pregnant women with MDE were no more likely than nonpregnant women to be diagnosed with or treated for their depression.