- Objectives To identify the adverse effect of psychiatric illness during pregnancy on pregnancy outcome. Methods A large population-based study of deliveries (1988–2005) was conducted that compared women with and without psychiatric illness. Stratified analysis included multiple logistic regression models. Results Out of 181,479 deliveries, 607 (0.3%) women reported psychiatric illness: depressive and anxiety disorders (39%), schizophrenia (11%), or other psychiatric illness (50%). The psychiatric patients were significantly older, with higher prevalence of diabetes and hypertensive disorders. Perinatal mortality rate, congenital malformations, low Apgar scores, and low birth weight (< 2500 g) were significantly increased. Multivariable logistic regression models determined that psychiatric illness during pregnancy is an independent risk factor for perinatal mortality (odds ratio [OR] 2.4; 95% CI, 1.5–3.7, P < 0.001) and congenital malformations (OR 1.4; 95% CI, 1.01–1.9, P = 0.03). Conclusions Psychiatric illness is an independent risk factor for congenital malformations and perinatal mortality, and prenatal care should be adjusted accordingly.