Group B Strep Screening

GBS colonisation is usually silent; the neonatal risk is created by timing. Streptococcus agalactiae normally inhabits the gastrointestinal and genitourinary tracts, and maternal rectovaginal colonisation provides the reservoir for transmission during labour or after the membranes rupture. The newborn may then develop early-onset pneumonia, sepsis, or meningitis. Colonisation is transient and intermittent, so a screening culture is a time-limited snapshot rather than a permanent label. In Canada, screening is offered at 35–37 weeks, including when a caesarean birth is planned, because labour or membrane rupture may occur before the scheduled operation. The bedside decision has two separate parts: determine whether intrapartum antibiotic prophylaxis (IAP) is indicated, then determine whether it was adequate for newborn risk assessment. At least 4 hours before birth is the adequacy threshold for IV penicillin G, ampicillin, or cefazolin; clindamycin and vancomycin can be the correct maternal choices for some allergies but are still classified as inadequate for this neonatal assessment. Necessary obstetric care must not be delayed solely to complete 4 hours. A symptomatic newborn requires immediate sepsis management regardless of the maternal screening result.