A population-based cohort study in Sweden suggests prenatal antibiotic exposure is associated with increased risk of group B Streptococcus (GBS) disease in newborns, researchers reported last week in the Journal of Infection.
The study, led by researchers at Sweden’s Karolinska Institutet, used four Swedish national registries to examine prenatal antibiotic exposure during all singleton live births in Sweden from 2006 to 2016. Although intrapartum antibiotic prophylaxis (prevention), guided by risk-based strategies, was implemented by Sweden in 2008 to prevent GBS transmission from mother to newborn during the intrapartum period (all stages of labor and delivery) and reduce early-onset GBS disease, GBS still accounts for 40% of severe early-onset infections in Swedish newborns. Some research has suggested a moderately increased risk of infection in children who had prenatal antibiotic exposure.
“Given the widespread use of antibiotics during pregnancy (~25% of pregnancies globally), rising GBS resistance, and the lack of licensed maternal GBS vaccine, this potential association warrants further studies,” the study authors wrote.
29% increased risk of GBS disease in antibiotic-exposed newborns
Among 1,095,644 liveborn singletons, prenatal antibiotic exposure was recorded in 24.5%, of which 4.9% were exposed in more than one trimester. During the study period, the overall incidence of GBS disease was 0.71 per 1,000 live births.
Compared with unexposed newborns, GBS incidence within four weeks postpartum was higher among exposed newborns (0.86 vs 0.66 per 1,000 live births), for an increased risk of 29% (adjusted odds ratio [aOR], 1.29). Among pregnancies without any GBS risk factors, prenatal antibiotic exposure was associated with a 34% higher risk of GBS disease (aOR, 1.34), while no association was observed among pregnancies with at least one risk factor (aOR, 0.91). The strongest association was observed with early third-trimester antibiotic exposure (aOR, 1.67).
Although the authors say it’s too early to draw causal conclusions and further confirmation of the association is needed, they suggest the findings hint at a possible mechanism involving antibiotic-induced disruption of the maternal microbiota, particularly a decline in Lactobacillus species, which dominate the vaginal microbiome and help prevent GBS colonization.
“Studies with detailed intrapartum antibiotic data and dose-response analyses are needed to provide a more complete picture of this important topic,” they wrote.
