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.