BACKGROUND: Group B Streptococcus (GBS) infection is a leading cause of neonatal morbidity. Maternal rectovaginal GBS colonization is a primary risk factor for early onset neonatal GBS infection. In Belgium, pregnant women are screened and, if positive or at risk of transmission, offered intrapartum antibiotic prophylaxis (IAP). We aimed to provide the first comprehensive overview of Belgian data and identify possible risk factors of maternal GBS colonization and neonatal infection.

METHODS: We calculated proportions of maternal screening, colonization and incidence of all neonatal GBS infections and identified their risk factors using log binomial regression from national registries’ data between 2012-2021.

RESULTS: Of all women, 90.2% were screened and of them, 18.5% were GBS colonized. These proportions were stable over time. Risk factors for maternal GBS colonization included Sub-Saharan (aRR = 1.45, [1.41-1.48]) and North-African origin (aRR = 1.31, [1.28-1.34]) and 5 + parity (aRR = 1.21, [1.18-1.25]). Neonatal GBS sepsis incidence showed a gradually decreasing trend in two individual data sources. Flanders’ overall neonatal GBS sepsis estimates were around 0.49 cases per 1000 livebirths. Risk factors for neonatal GBS infection included preterm birth (aRR = 7-41, depending on level of prematurity) and very low birthweight (aRR = 14.83, [6.48-33.94]). Babies of colonized women were at higher risk without (aRR = 7.05, [5.05-9.85]) than with IAP (aRR = 4.34, [3.28-5.74]) compared to non-colonized women.

CONCLUSIONS: The maternal colonization rate and the neonatal GBS sepsis incidence in Belgium is comparable to European data. We identified already known risk factors and effectiveness of IAP. Mothers at risk for GBS colonization and premature/low birth weight deliveries could benefit most from additional maternal vaccination strategy.