In a study of 312 women with acute chorioamnionitis, 152 women received antibiotics before delivery, 90 received antibiotics after cord clamping, and 70 did not receive antibiotics. Antibiotics were administered during labor rather than after cord clamping if delivery was not imminent. Although endometritis developed more frequently in the patients receiving antibiotics after cord clamping, the difference was not statistically significant (5.6% versus 3.9%, difference not significant). There were two cases of verified sepsis in the group of infants (35 weeks) born to mothers receiving intrapartum antibiotics and there were eight cases in the no antibiotics group (p = 0.06). More importantly, in neonates greater than or equal to 35 weeks' gestational age, there was a significant difference in the frequency of positive blood cultures for group B streptococci (0/133 versus 8/140, p less than 0.05). We conclude that administration of antibiotics to the mother during labor may result in a decreased incidence of neonatal sepsis.