The effects of methadone on maternal-fetal interactions in the rat.

Female Sprague-Dawley rats received methadone (25 mg/kg/day) by gavage throughout gestation. Water-gavaged rats served as controls. Fetuses were delivered by cesarean section when parturition was imminent. Our results indicate that methadone may interfere with fetal development and maternal-fetal interactions to some degree. The observed alterations were as follows: fetal growth retardation, an interference with the triggering of parturition once normal delivery size is attained and possible positional malformations.