(586) Ampicillin–Gentamicin Versus Ampicillin Alone for Term PROM in GBS-Negative Patients: A Randomized Controlled Trial

Objective:
To compare maternal and neonatal outcomes between two prophylactic antibiotic regimens—ampicillin plus gentamicin versus ampicillin alone—in patients with term premature rupture of membranes (PROM) and confirmed negative group B Streptococcus (GBS) colonization.

Study Design:
This single-center, randomized controlled trial was conducted at a tertiary university-affiliated hospital between November 2022 and July 2025. Eligible participants were women with singleton term pregnancies, PROM >18 hours, and negative GBS colonization. Patients were randomized in a 1:1 ratio to receive either intravenous ampicillin (2g every 6h) plus gentamicin (5mg/kg every 24h) or ampicillin alone, starting 18 hours post-PROM. The primary outcome was the incidence of clinical chorioamnionitis. Secondary outcomes included intrapartum fever, postpartum maternal infections, postpartum stay ≥5 days, and neonatal morbidity. Chorioamniotic cultures were obtained postpartum. Analyses were performed on an intention-to-treat basis.

Results:
A total of 207 women were randomized (103 to ampicillin–gentamicin; 104 to ampicillin alone). Clinical chorioamnionitis occurred less frequently in the combination group (1.9% vs. 10.6%; p=0.019; number needed to treat = 11.5, 95% CI: 7–45). Postpartum infectious morbidity was also reduced in the ampicillin–gentamicin group (1.9% vs. 9.6%; p=0.033), as was the rate of postpartum hospitalization ≥5 days (3.9% vs. 13.5%; p=0.024) (Figure 1). Neonatal outcomes did not differ significantly between groups. Positive chorioamniotic cultures were less frequent in the ampicillin–gentamicin group (20.9% vs. 36.7%; p=0.029), including a lower prevalence of Enterobacteriaceae spp. (12.1% vs. 25.6%; p=0.033) (Figure 2).

Conclusion:

Among GBS-negative patients with prolonged term PROM, prophylactic administration of ampicillin plus gentamicin significantly reduced rates of clinical chorioamnionitis and postpartum maternal infectious morbidity compared to ampicillin monotherapy. Broader Gram-negative coverage may improve maternal outcomes and warrants further evaluation