ABSTRACT
Cord blood ampicillin levels were assayed in 23 neonates whose mothers received the antibiotic by the obstetrical service. The levels ranged from 2.9 to 36.2 μg/ml. Nineteen (82.6%) of the 23 had a serum ampicillin level in excess of 5 μg/ml at delivery, which is significantly greater than the minimal inhibitory concentration (MIC) to inhibit ampicillin-sensitive enterobacteriacae and far exceeds the MIC for Group B beta-hemolytic streptococci. Antenatal ampicillin therapy results in significant levels in the neonate that may obscure cultures obtained after delivery.
