Meta-Analysis Highlights Gestational Diabetes as Novel Risk Factor for Maternal GBS Transmission

This study reconciled previously conflicting findings and established that both gestational diabetes and pregestational diabetes are notable risk factors for maternal rectovaginal carriage of GBS.

"Recognizing GDM as a risk factor in clinical decisions regarding GBS screening and intrapartum antibiotic prophylaxis has the potential to reduce the global impact of GBS on maternal and perinatal health," the researchers wrote in BMC Pregnancy and Childbirth.

Maternal rectovaginal colonization by GBS raises the risk of perinatal GBS disease that can lead to death or long-term neurological impairment. The factors contributing to rectovaginal carriage of Group B Streptococcus are not fully understood, leading to challenges in identifying GBS through risk-based clinical approaches. There remains uncertainty regarding whether GDM constitutes a risk factor for rectovaginal GBS colonization.

To fill this knowledge gap, Kathryn A. Patras, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA, and colleagues aim to address current conflicting findings and determine whether GDM should be clinically considered as a risk factor for maternal GBS colonization by conducting a systematic review and meta-analysis.

The analysis included peer-reviewed studies that provided GDM prevalence and documented GBS vaginal and/or rectal colonization in women with and without gestational diabetes. From the study's inception to October 30, 2023, the researchers identified 6,275 relevant studies from online databases of which 19 were eligible for inclusion.

The eligible studies underwent analysis and rigorous evaluation for bias risk using a modified Newcastle-Ottawa Scale. This assessment included considerations of cohort representativeness, comparability, quality of reporting on GDM and GBS status, and potential bias related to other metabolic conditions. The synthesized results were analyzed using STATA 18 software and subjected to random-effects meta-analyses.

The researchers reported the following findings:

· Studies encompassed 266,706 women from 10 different countries, with study periods spanning from 1981 to 2020.

· Meta-analysis revealed that gestational diabetes is associated with a 16% increased risk of rectovaginal GBS carriage (OR 1.16).

· Subgroup analyses were also performed to assess the independent effects of pregestational vs. gestational diabetes on the risk of maternal GBS carriage.

· Pregestational diabetes (Type 1 or Type 2 diabetes mellitus) was also associated with an increased risk of 76% (pooled OR 1.76).

"An important future focus is to evaluate neonatal infection rates among women with GDM and investigate whether optimal glucose management contributes to reducing GBS-related morbidity and mortality in newborns," the researchers concluded.

"Enhancing our understanding of other factors influencing GBS transmission to neonates will enhance screening, prevention, and treatment strategies for fetal and neonatal GBS disease."

Reference:

Mercado-Evans, V., Zulk, J.J., Hameed, Z.A. et al. Gestational diabetes as a risk factor for GBS maternal rectovaginal colonization: a systematic review and meta-analysis. BMC Pregnancy Childbirth 24, 488 (2024). https://doi.org/10.1186/s12884-024-06694-7