Postnatal antibiotic exposure due to maternal group B streptococcus is associated with childhood asthma

Previous studies identified early-life antibiotic exposure as a risk factor for childhood asthma. However, this association may be confounded by an indication, as antibiotics are often prescribed for respiratory infections, which themselves promote asthma. To mitigate this bias, we aim to assess the unique contribution of postnatal antibiotic therapy, given to non-infected infants for maternal indication, on childhood asthma risk.

We screened electronic medical records to identify healthy full-term infants born during 2006-2018 to mothers with a positive group B streptococcus (GBS) vaginal culture. Infants with postnatal respiratory symptoms/pneumonia or positive blood/cerebrospinal fluid cultures were excluded. The primary outcome was an asthma diagnosis by age 6 years. We fitted a multivariable quasi-Poisson regression model to assess the unique contribution of antibiotic treatment to asthma diagnosis. As a validation step, we utilized a propensity model in which infants treated with antibiotics were matched 1:3 with infants not treated.

The cohort included 14,807 infants, of whom 311 received antibiotics. After controlling for potential confounders, postnatal antibiotic exposure was associated with higher asthma risk (adjusted risk ratio [aRR] = 1.3, 95%; confidence interval [CI] 1.04-1.61, p = .017). Higher asthma risk was validated in the propensity model (aRR = 1.49, 95% CI 1.12-1.96 p = .005). Postnatal antibiotic therapy was also associated with secondary outcomes such as the short-acting beta-ag use (aRR = 1.13, 95% CI 0.99-1.28, p = .072) and allergic rhinitis diagnosis (aRR = 3.00, 95% CI 1.43-6.30, p = .003).

Postnatal antibiotic therapy administrated for maternal GBS, not confounded by infants' infections, was associated with higher childhood asthma risk.