Group B Streptococcus maternal colonization and respiratory infections in the offspring: lessons learned from an analysis of a population-based cohort with 18-year follow-up

Objective: Group B Streptococcus (GBS) early onset disease is a major cause for neonatal morbidity and mortality. We aimed to determine whether maternal GBS and the associated intrapartum antibiotic prophylaxis impacts pediatric long-term respiratory infectious morbidity. Study design: A population-based cohort study was conducted, during the years 1991–2013, comparing the incidence of hospitalizations due to common respiratory infections (RI) in offspring of mothers with and without GBS. Univariate analysis and a Cox proportional hazard model were used to estimate un-adjusted and adjusted hazard ratios for pediatric RI risk. Results: During the study period, 173,757 term vaginal deliveries took place, of which 2.4% (4252) were diagnosed as GBS + gravidas. In univariate and multivariate analyses for the entire study period, RI risk was increased in exposed offspring. In a sensitivity analysis investigating study periods with different health policies, both GBS diagnosis rates and pediatric infectious respiratory morbidity rates increased over time, but with no independent association between the two. Conclusion: When analyzing large data sets spanning over long time periods, a special attention must be paid to account for healthcare trends, to avoid erroneous conclusions, as demonstrated here.