GBS infection is the leading cause of neonatal infection and the major cause of sepsis in newborns. It is also recognized as an important cause of maternal uterine infection and septicemia. Vertical transmission of GBS during labor and delivery may result in early-onset GBS invasive infection, resulting in approximately 1600 cases and 80 deaths annually. ACOG, the American Academy of Pediatrics, and the Centers for Disease Control and Prevention (CDC) have collaborated to advise that all obstetric providers use either culture-based or risk-based screening approaches for the prevention of early-onset neonatal GBS. Vaginal and rectal culture-based methods recommend universal prenatal screening for GBS colonization in women at 35-37 weeks' gestation. Between 10% and 30% of pregnant women are colonized with GBS in the vagina or rectum.[24,25] Women with GBS colonization should receive intrapartum antibiotic prophylaxis for perinatal GBS disease prevention.
Women whose culture results are unknown at the time of delivery should be managed according to the risk-based approach. Gestation at <37 weeks, duration of membrane rupture of ≥18 hours, or temperature of ≥100.4 ºF (≥38.0 ºC) are clinical indications for intrapartum prophylaxis if the GBS status is unknown at the time of delivery. Intrapartum prophylaxis is also indicated for women with GBS bacteriuria during their current pregnancy or those with previous delivery of an infant with invasive GBS disease.
The narrow-spectrum agent, penicillin G (5 million units [as the potassium or sodium salt] i.v., followed by 2.5 million units every 4 hours until delivery), remains the antibiotic of choice for intrapartum prophylaxis.[23,26] Ampicillin (2 g [as the sodium salt] i.v., followed by 1 g every 4 hours until delivery) is an acceptable alternative, but it may increase the incidence of ampicillin-resistant E. coli in neonates.[6,7] Penicillin G or ampicillin is most effective when initiated at least 4 hours before delivery. For patients who are allergic to penicillin and not at high risk for anaphylaxis, cefazolin (2 g [as the sodium salt] i.v., followed by 1 g every 8 hours until delivery) is recommended. Per the recommendations from CDC, patients who are penicillin allergic and at high risk for anaphylaxis may be given clindamycin (900 mg [as the phosphate ester] i.v. every 8 hours until delivery) or erythromycin (500 mg [as the lactobionate salt] i.v. every 6 hours until delivery) as long as GBS susceptibility has been confirmed. Increasing resistance of GBS isolates to clindamycin and erythromycin has been reported, making it necessary to obtain susceptibility reports before using these agents. Of note, erythromycin does not cross the placenta; therefore, clindamycin may be the preferred choice over erythromycin to achieve adequate concentrations in the fetal circulation. In the event of GBS isolates resistant to clindamycin or erythromycin, or if the susceptibility is unknown, vancomycin (1 g [as the hydrochloride salt] i.v. every 12 hours until delivery) must be used.
Am J Health Syst Pharm. 2006;63(11):1038-1047. © 2006 American Society of Health-System Pharmacists
Cite this: Drug Therapy During Labor and Delivery, Part 1 - Medscape - Jun 01, 2006.