Group B Streptococcus and pregnancy outcomes: a retrospective study of 20,040 cases

To investigate the association between maternal Group B Streptococcus (GBS) colonisation in late pregnancy and pregnancy outcomes, with a focus on GBS colonisation risk factors and the role of colonisation density in influencing maternal and neonatal health.

This retrospective study analysed clinical data from 20,040 pregnant women at 35-37 weeks of gestation between January 2020 and January 2023. GBS colonisation was assessed using rectovaginal swabs, followed by culture, PCR quantification, and antibiotic susceptibility testing. Demographic and clinical characteristics, maternal outcomes, and neonatal outcomes were compared between GBS-positive and GBS-negative groups. Further stratified analysis was conducted on the impact of high GBS colonisation on maternal and neonatal outcomes. Logistic regression was used to identify independent risk factors for GBS colonisation.

GBS colonisation was detected in 505 of 20,040 women (2.52%). Among the 236 isolates tested, all were sensitive to penicillin. Significant risk factors for GBS colonisation included maternal age ≥35 years, gestational diabetes mellitus, and coexisting vaginitis (p < 0.05). The incidence of puerperal infection, PROM, postpartum haemorrhage, premature birth, and neonatal pneumonia were significantly higher in the GBS-positive group than in the GBS-negative group (p < 0.05). Stratification by colonisation density revealed that women with high GBS colonisation had elevated rates of puerperal infection (23.01% vs. 14.29%), PROM (34.51% vs. 19.13%), and postpartum haemorrhage (18.58% vs. 8.93%) compared to those with lower GBS colonisation (p < 0.05). Neonatal outcomes also varied by colonisation density: neonatal infection (14.16% vs. 6.89%) and premature birth (16.81% vs. 9.69%) were significantly more common in the high-colonisation group.

Maternal GBS colonisation, especially with high density, increases adverse outcomes. Risk factors include age ≥35, vaginitis, and diabetes. Routine screening and targeted prophylaxis are essential.