BackgroundThe effects of in utero exposure to atypical antipsychotics on infant birth weight are unknown.AimsTo determine whether atypical and typical antipsychotics differ in their effects on birth weight after maternal exposure during pregnancy.MethodProspective data on gestational age and birth weight collected by the National Teratology Information Service for infants exposed to typical (n=45) and atypical (n=25) antipsychotics was compared with data for a reference group of infants (n=38).ResultsInfants exposed to atypical antipsychotics had a significantly higher incidence of large for gestational age (LGA) than both comparison groups and a mean birth weight significantly heavier than those exposed to typical antipsychotics. In contrast those exposed to typical antipsychotics had a significantly lower mean birth weight and a higher incidence of small for gestational age infants than the reference group.ConclusionsIn utero exposure to atypical antipsychotic drugs may increase infant birth weight and risk of LGA.