The proportion of GBS-positive mothers among the screened population and outcomes of maternal Group B streptococcus colonization at King Saud University Medical City: a retrospective cohort study.

Abstract

Background: Group B Streptococcus (GBS) is a leading cause of neonatal morbidity, preventable via intrapartum antibiotic prophylaxis (IAP).

Objective: To determine the proportion of GBS-positive mothers among the screened population, evaluate IAP protocol adherence, and identify clinical risk factors and outcomes.

Design: Single-center retrospective cohort study.

Settings: Labor and Delivery Suite at King Saud University Medical City (KSUMC), Riyadh.

Patients and methods: Electronic medical records (July 2021-December 2022) were reviewed for pregnant women (≥35 weeks) who were screened or had GBS bacteriuria, along with their neonates. Multivariate logistic regression was used to determine risk factors.

Main outcome measures: Proportion of GBS-positive mothers among the screened population, IAP timing, maternal febrile morbidity, neonatal intensive care unit (NICU) admissions, and culture-positive sepsis.

Sample size: Of the 5292 deliveries, 688 unscreened elective cesareans were excluded, leaving 4604 screened women and 180 GBS-positive dyads.

Results: The proportion of GBS-positive mothers among the screened population was 3.91% (180/4604). Although 67.2% (121/180) of colonized women received IAP, only 15.6% (28/180) received it ≥4 hours before delivery. Maternal febrile morbidity was 0% (0/180). The neonatal intensive care unit (NICU) admission rate was 8.3% (15/180), and culture-positive neonatal sepsis occurred in 1.1% (2/180) of cases. GBS bacteriuria independently predicted adverse neonatal outcomes (aOR 2.35, 95% CI: 1.12-4.92, P=.024), while preterm delivery showed a negative correlation (aOR 0.29, 95% CI: 0.11-0.76, P=.012).

Conclusions: The proportion of GBS-positive mothers in the screened population is low (3.91%). While perinatal outcomes were generally excellent regardless of antibiotic timing, GBS bacteriuria was identified as a significant, independent predictor of adverse neonatal outcomes. These findings highlight a biologically plausible risk pathway that warrants validation in larger, multi-center prospective studies.