OBJECTIVE: This study was undertaken to provide information on the prevalence of use of antidepressant drugs among pregnant women in the United States. STUDY DESIGN: A retrospective study was conducted using the automated databases of 7 health plans. Women who delivered an infant in a hospital were identified. Antidepressant drug use was evaluated assuming a gestational duration of 270 days. RESULTS: Among the 118,935 deliveries occurring from 2001-2005, 6.6% of women were dispensed an antidepressant during pregnancy. Antidepressant drug use increased from 2.0% in 1996 to 7.6% of deliveries in 2004 and 2005. Selective serotonin reuptake inhibitor use increased from 1.5% in 1996 to 6.4% in 2004 and 6.2% in 2005. CONCLUSION: Our finding that nearly 8% of pregnant women were prescribed antidepressants drugs during the years 2004 and 2005 highlights the importance of understanding the effects of these medications on the developing fetus and on the pregnant woman.