Antibiotic prophylaxis for presumptive group B streptococcal infection in preterm premature rupture of the membranes: effect on neonatal and maternal infectious morbidity.

Objective: The purpose of this study was to determine if the prevalence of neonatal and maternal infectious morbidity in patients with preterm premature rupture of membranes (PROM) who received ampicillin prophylaxis for presemptive group B streptococcal colonization is increased compared to those who received no prophylaxis.
Methods: The charts of all patients with preterm PROM who delivered between January 1988 and December 1993 were retrospectively reviewed. The routine use of ampicillin prophylaxis was initiated in January 1991. Patients with singleton gestations were included in the analysis only if chorioamnionitis was excluded on admission. Variables used in the final analysis included gestational age at the time of preterm PROM, gestational age at delivery, duration of rupture of membranes, birth weight, method of delivery, use of steroids, tocolytics, or antibiotics for group B streptococcus prophylaxis, neonatal sepsis, neonatal mortality, and postpartum endomyometritis. Data were analyzed using Student's t-test, chi-square test, Fisher's exact test, and stepwise logistic regression analysis to evaluate the effect of chemoprophylaxis for group B streptococcus on the incidence of neonatal sepsis and maternal postpartum endomyometritis. A two-tailed P < 0.05 was used to denote statistical significance.
Results: The charts of 206 patients were reviewed; 146 patients received ampicillin for group B streptococcal prophylaxis and 60 patients did not. There was a significantly higher incidence of postpartum endomyometritis among the patients who received ampicillin (62% vs. 22%; P < 0.01). The association between postpartum endomyometritis and chemoprophylaxis remained significant even after controlling for other confounding variables. There was no significant difference in the incidence of neonatal sepsis (5% vs. 7%; P = 0.7) or death (5% vs. 3%; P = 0.9) between both groups.
Conclusions: Group B streptococcal prophylaxis with a short course of intravenous ampicillin increases the risk of postpartum endomyometritis in patients with premature PROM.