Neonatal Sepsis and Outcomes of Maternal Group B Streptococcus Colonization in Preterm Birth

Objectives: To evaluate the association between maternal group B Streptococcus (GBS) colonization in preterm birth and neonatal outcomes.Materials and Methods: A single-center retrospective paired cohort study was conducted at Chonburi Hospital, Thailand, from January 2014 to December 2024. Pregnant women admitted with preterm labor and delivery who underwent recto-vaginal swab culture were included. Pregnant women were categorized into two group based on GBS cultured status. Maternal and neonatal outcomes were compared between group. For adjusted analyses, GBS-positive mothers were matched 1:1 with GBS-negative mothers by year of recto-vaginal swab collection and gestational age at delivery. Logistic regression was performed to identify independent risk factors for neonatal sepsis in paired cohort. Results: Among 3,895 women with preterm delivery, 114 mothers (2.9%) were colonized with GBS, accounting for 123 neonates. In the unpaired analysis, neonatal sepsis did not differ significantly between neonates born to GBS-positive and GBS-negative mothers (33.9% vs 36.5%, p = 0.556). The rate of stillbirth occurred more among GBS-positive mothers. In the paired cohort of 114 matched maternal pairs and their neonates, maternal GBS colonization was not independently associated with neonatal sepsis or other neonatal morbidities. Multivariable analysis identified lower gestational age and birth weight between 1.5–2.5 kg as an independent risk factors for neonatal sepsis.Conclusion: Maternal GBS colonization in preterm birth was not an independent risk factor for neonatal sepsis. Neonatal sepsis was primarily related to prematurity-associated factors, while stillbirth was more frequent among GBS-positive mothers.