Duration of Intrapartum Antibiotic Prophylaxis for Group B Streptococcus [06A]

Abstract

INTRODUCTION: Intrapartum vertical transmission of group B streptococcus (GBS) occurs in approximately 50% of vaginal births without antibiotic prophylaxis. This prospective cohort study aimed to determine if <4 hours duration of intrapartum antibiotic prophylaxis (IAP) before delivery reduces GBS vertical transmission rates. METHODS: 1354 GBS positive parturients presented to Yale New Haven Hospital between 10/1/2009 and 3/28/2012. Of eligible patients ≥37 weeks with singleton gestations in labor (n=1111), 316 were invited after IRB approval to participate and 240 completed the study. Maternal characteristics, labor course, delivery and neonatal outcomes were obtained. Of 240 maternal-infant dyads, 69 received <4 hours of IAP and 158 received ≥4 hours. Nine did not receive IAP. Infant oropharyngeal and rectal swabs were collected after 24 hours to detect mucosal GBS colonization. RESULTS: Rates of GBS transmission were equivalent in those receiving less than and greater than 4 hours of prophylaxis before delivery, respectively (1.5 vs 1.2%; P=1.0). No significant differences in GBS transmission were observed between those with and without risk factors for early neonatal GBS disease. No cases of GBS vertical transmission occurred in those who received IAP prior to membrane rupture versus 3 (3.9%) cases of transmission (P=.036) among those who received IAP after membrane rupture. CONCLUSION: GBS vertical transmission rates among individuals who received IAP <4 hours were equivalent to those receiving IAP ≥4 hours before delivery. Antibiotic prophylaxis duration may be less relevant than membrane rupture timing in vertical transmission and deserves further exploration to optimize newborn monitoring protocols after delivery in maternal GBS colonization.