Selective intrapartum prophylaxis for group B streptococcus colonization: management and outcome of newborns.

OBJECTIVE

Intrapartum antibiotic prophylaxis (IAP) in mothers with group B streptococcus (GBS) colonization presents difficult neonatal management decisions. IAP was instituted in response to an increased incidence of early-onset GBS sepsis (EOGBSS), and a study was conducted to evaluate the outcome of these newborns.

METHODS

A study was undertaken at Truman Medical Center-East, a county hospital with a level 1 nursery. During the 20-month study period, prenatal GBS cultures were obtained on all mothers in their third trimester of pregnancy. At time of delivery, GBS-positive women who had at least one risk factor were to receive IAP. Risk factors included fever and/or amnionitis, premature labor, and prolonged rupture of membranes defined as > 6 hours. Screening laboratory tests were performed on all newborns whose mothers received IAP. Only the newborns with positive screening laboratory tests or symptoms of sepsis received further laboratory evaluation and antibiotic treatment.

RESULTS

During the study, 2040 mothers gave birth to 2054 newborns. Three hundred thirty-two mothers (16.3%) were colonized with GBS and 122 (37.0%) had at least one risk factor. IAP was given to 70 GBS-positive mothers. Thirty-three (27%) GBS-positive mothers with risk factors did not receive IAP for logistical reasons. Eleven full-term newborns had EOGBSS: For case newborns, the mean duration of ruptured membranes was 13.7 hours (range 2.5 to 28 hours). Vertical transmission occurred as follows: Cutaneous colonization was found in 33 (12.5%) newborns born to 261 mothers who received no IAP, and symptomatic EOGBSS was diagnosed in 9 (3.4%). Mothers who received one dose (n = 43) had three (6.9%) newborns with GBS colonization and two (4.7%) asymptomatic newborns with EOGBSS: No newborns born to 28 mothers who received two doses IAP had GBS colonization or were ill. Cutaneous vertical transmission was reduced (P = .03). Newborns born to GBS-positive mothers with one or more risk factors who received IAP had significantly less EOGBSS (P < .05) than those who did not receive IAP.

CONCLUSIONS

Selective IAP was administered safely to 21% of GBS-positive women, or 3.5% of all deliveries. IAP prevented EOGBSS when it could be given to GBS-positive mothers with a risk factor. Accurate identification of mothers with GBS colonization and their risk factors is essential for effective use of IAP. Earlier institution of IAP after rupture of membranes may reduce the risk of EOGBSS and the need for extensive infant evaluation.