Objective: To identify limitations of current strategies for intrapartum prophylaxis of neonatal early-onset group B streptococcal infection.
Methods: Retrospective review of infants with culture-proven early-onset group B streptococcal infection admitted to two nurseries and their mothers from July 1992, when ACOG and AAP guidelines for intrapartum prophylaxis were first issued, through December 2001. Information was recorded regarding clinical risk factors for early-onset group B streptococcal infection, collection and processing of specimens to assess maternal colonization, delivery of prophylaxis, duration of hospitalization before delivery, and outcome.
Results: Among 92 infants with early-onset group B streptococcal infection admitted from 23 institutions, 68 had received no intrapartum prophylaxis. Of these 68 who received no prophylaxis, 34 had identifiable risk factors before delivery (32 clinical, two positive maternal culture), while 34 had no risk factors. Prenatal culture for group B streptococcal colonization was performed in 22 of these women. Of the 18 cultures that were negative for group B streptococcus, 15 were obtained using suboptimal culture technique or were collected more than 6 weeks before delivery. Of the 68 with no prophylaxis, 14 required extracorporeal membrane oxygenation and three died. Of the 24 who received some intrapartum prophylaxis, nine had received >/=two doses for >/=4 hours immediately before delivery. Among the 24 receiving some intrapartum prophylaxis, two required extracorporeal membrane oxygenation and one died. No deaths occurred in those who received >4 hours of prophylaxis, although one such infant required extracorporeal membrane oxygenation. After the CDC guidelines were issued in May 1996, there was a decrease both in the number of cases of early-onset group B streptococcal infection (56 versus 36) as well as in the number with clinical risk factors but no intrapartum prophylaxis (24/56 (43%) versus 5/28 (18%)).
Conclusions: The use of clinical risk factors alone will inevitably result in missed opportunity for intrapartum antibiotic prophylaxis. With maternal screening, false-negative results will be reduced but not necessarily eliminated by assuring that specimens are obtained from proper sites using selective media within 6 weeks of delivery. Better strategies are needed to assure timely administration when prophylaxis is indicated. The nine neonates with early-onset group B streptococcal infection despite intrapartum antibiotics for the recommended duration illustrate that disease may occur even when guidelines are implemented appropriately.