Background Early-onset group B Streptococcus disease (EOGBS) remains a leading cause of neonatal morbidity and mortality. While intrapartum antibiotic prophylaxis based on clinical risk factors is widely implemented for prevention, emerging evidence suggests that maternal body mass index (BMI) may be an independent risk factor. This systematic review and meta-analysis evaluated the association between maternal BMI and the risk of EOGBS, as well as related proxy outcomes, including intrapartum vaginal GBS (Group B Streptococcus) and rectovaginal/urinary GBS colonization before term.

Methods We systematically searched MEDLINE, Embase, and Cochrane CENTRAL on the 5th of August 2024, for studies examining the relationship between pregestational BMI and EOGBS or its proxy outcomes. Eligible studies included observational and interventional designs, excluding case reports and conference abstracts. Risk of bias was assessed using the QUIPS tool. Random-effects meta-regression and sensitivity analyses were performed.

Results We identified 16 eligible observational studies reporting data from a total of 2,621,817 women, encompassing 77,809 cases. For the risk of EOGBS and its proxy outcomes, our meta-regression showed a 2.7% increase in the odds ratio (OR) per unit increase in BMI. This corresponds to an OR of 1.4 (95% CI 1.1-1.7) for a BMI of 35 and 1.7 (95% CI 1.2-2.5) for a BMI of 45, compared to a normal BMI of 22. Sensitivity analyses by crude estimates showed an increase in the OR of 3.6% per unit increase in BMI, corresponding to an OR of 2.2 (95% CI 1.4-3.6) for a BMI of 45. One very large study on 1,971,346 live singleton births with 780 EOGBS cases, found a hazard ratio of 2.4 (95% CI 1.7-3.4) for a BMI of 35.0–39.9 compared to normal BMI.

Conclusions Although the overall association appears modest, incorporating BMI may enhance prevention strategies for EOGBS.

This study protocol was registered in PROSPERO (CRD42023439201).

The authors have declared no competing interest.

The author(s) received no specific funding for this work.

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