Intrapartum Chemoprophylaxis for Group B Streptococcus Infection to Prevent Neonatal Disease: Who Should be Treated?

Abstract

The purpose of this study was to examine the maternal risk factors associated with early onset Group B streptococcus (GBS) sepsis and determine the potential impact of intrapartum chemoprophylaxis using these risk factors. Using a computerized perinatal database, 26,525 deliveries over a five-year period (1989 to 1994) were identified. Neonates with GBS-positive cultures were identified and the neonatal and maternal chart of each case was reviewed. Twenty-six neonates (1 of 1000) had GBS sepsis documented by blood or cerebrospinal fluid culture. Maternal risk factor(s) were identified in 13 (50%) cases: preterm labor (5), preterm premature rupture of the membranes (5), prolonged rupture of membranes (6), sibling affected by symptomatic GBS infection (2), or maternal fever during labor (5). There were four mothers whose neonates had GBS sepsis in spite of intrapartum antibiotics. Intrapartum chemoprophylaxis for GBS based on risk factors alone will identify only half of the neonates who develop disease. Extension of intrapartum chemoprophylaxis to patients with risk factors appears to be necessary to prevent early onset disease in the other half. Since 85.7% of our total obstetrical population has no risk factors, this policy would require treating 1749 women to prevent one case of GBS sepsis. Chemoprophylaxis could be more appropriately targeted if mothers colonized with GBS could be identified in early labor.

Risk Factors for Early-onset Group B Streptococcal Sepsis: Estimation of Odds Ratios by Critical Literature Review

“…Although having had a previous infant with invasive GBS disease is accepted widely as placing a mother at high risk in subsequent pregnancies, only four instances have been reported in which neonatal GBS infection followed more than one pregnancy in the same mother. [137][138][139] We have seen other instances of this event, so it probably is not as unusual as is suggested by the rarity of reported cases. Women may remain colonized with the same strain of GBS for prolonged periods 140 and may fail to develop protective levels of type-specific serum antibodies despite long-term colonization.…”

Prevention of early onset neonatal group B streptococcal infection

“…17 However, subsequent studies have shown that only approximately 50% of mothers with infants who developed neonatal disease had identifiable risk factors. [18][19][20] Thus, a clinical risk factor based approach would lead to unnecessary treatment of a large number of women and, more importantly, would fail to prevent around 50% of cases.…”