Objective: To compare the prevalence and clinical characteristics of neonatal abstinence syndrome in neonates exposed and not exposed to selective serotonin reuptake inhibitors (SSRIs) in utero. Design: Cohort study. Setting: Tertiary care center. Patients: One hundred twenty term infants, of whom 60 had prolonged in utero exposure to SSRIs, including paroxetine hydrochloride, fluoxetine, citalopram hydrobromide, sertraline hydrochloride, and venlafaxine hydrochloride. Main Outcome Measures: Neonatal abstinence syndrome was assessed with the Finnegan score as follows: score of 8 or above, severe; score of 4 to 7, mild; and score of 0 to 3, normal. All infants were followed up with a standardized protocol that included repeated Finnegan score assessments and cardiorespiratory monitoring until normalization of the Finnegan score. Results: Of the 60 neonates exposed to SSRIs in utero, 8 showed severe and 10 showed mild symptoms of a neonatal abstinence syndrome. All nonexposed neonates had a normal Finnegan score. In neonates who developed severe symptoms, the maximum mean daily Finnegan scores were recorded within 2 days after birth, although maximum individual scores were recorded as long as 4 days after birth. Conclusions: Neonatal abstinence syndrome occurs in 30% of neonates exposed to SSRIs in utero. These neonates should be monitored for at least 48 hours after birth. The long-term effects of prolonged exposure to SSRIs, particularly in neonates who develop severe symptoms, have yet to be determined.