Mental development in late infancy after prenatal exposure to benzodiazepines--a prospective study.

Seventeen infants born to mothers who used benzodiazepines (BZD) throughout pregnancy were followed prospectively and compared with 29 infants born to mothers who had not used psychoactive substances. On the Griffiths' Developmental Scale, the BZD-exposed infants demonstrated consistently lower mean GQs and DQs for all subscales at 5, 10 and 18 months of age. The differences in GQ reached statistical significance at 10 and 18 months. The DQs differed significantly for all subscales at 10 months and for the personal-social behaviour and hearing and speech subscales at 18 months of age. We suggest that prenatal exposure to BZD may cause a general delay in mental development up to 18 months of age.