Miller JE, et al. - This study was designed to determine the link between maternal antibiotic exposure before and during pregnancy, and risk of childhood hospitalization with infection. Antibiotic exposure before or during pregnancy was found to be associated with increased risk of childhood hospitalized infections. The suggested possible contributory mechanisms included alteration of the maternally derived microbiome and shared heritable and environmental determinants.

• Researchers used population-based Danish national databases for pregnancies between 1995 and 2009.
• They followed infants from birth until their first infection-related hospitalization, death, 14th birthday, emigration or end-2009.
• Exposure was maternal antibiotics prescribed before and during pregnancy.
• Infection-related hospitalization was the outcome.

• Antibiotic was prescribed for 141 359 (18%) mothers at least once during pregnancy, and for 230 886 (29.4% of those with complete data) in the 18 months before pregnancy.
• Findings revealed that out of 776 657 live-born singletons, 443 546 infection-related hospitalizations occurred in 222 524 (28.6%) children.
• An association was evident, between pregnancy antibiotic exposure and increased risk of childhood infection-related hospitalization [hazard ratio (HR) 1.18, 95% confidence interval (CI) 1.17–1.19].
• Researchers found that in mothers prescribed antibiotics only during pregnancy whose child did not receive pre-hospitalization antibiotics, this link was present only in those born vaginally.
• Data showed higher risks of infection-related hospitalization in cases where pregnancy antibiotic prescriptions were closer to birth and in mothers receiving more pregnancy antibiotics.
• In addition, an increased risk of infection-related hospitalization was observed in children born to mothers exposed to antibiotics before (but not during) pregnancy (HR 1.10, 95% CI 1.07–1.12).