%0 Journal Article %A Keely Loewen %A Barret Monchka %A Salaheddin M Mahmud %A Geert ‘t Jong %A Meghan B. Azad %T Prenatal antibiotic exposure and childhood asthma: a population-based study %D 2018 %R 10.1183/13993003.02070-2017 %J European Respiratory Journal %P 1702070 %X Antibiotic use during infancy alters gut microbiota and immune development and is associated with an increased risk of childhood asthma. The impact of prenatal antibiotic exposure is unclear. We sought to characterise the association between prenatal antibiotic exposure and childhood asthma.We performed a population-based cohort study using prescription records, hospitalization records, and physician billing claims from 213,661 mother-child dyads born in Manitoba, Canada from 1996–2012. Associations were determined using Cox regression, adjusting for maternal asthma, postnatal antibiotics, and other potential confounders. Sensitivity analyses evaluated maternal antibiotic use before and after pregnancy.36.8% of children were prenatally exposed to antibiotics, and 10.1% developed asthma. Prenatal antibiotic exposure was associated with an increased risk of asthma (adjusted HR 1.23, 95%CI 1.20–1.27). There was an apparent dose-response (aHRs: 1.15, 1.11–1.18 for 1 course; 1.26, 1.21–1.32 for 2 courses; 1.51, 1.44–1.59 for ≥3 courses). Maternal antibiotic use during 9 months before pregnancy (1.27, 1.24–1.31) and 9 months postpartum (1.32, 1.28–1.36) were similarly associated with asthma.Prenatal antibiotic exposure was associated with a dose-dependent increase in asthma risk. However, similar associations were observed for maternal antibiotic use before and after pregnancy, suggesting the association is either not directly causal, or not specific to pregnancy.Maternal antibiotic use is associated with childhood asthma, but the association is not specific to antibiotic use during pregnancyFootnotesThis manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.Conflict of interest: Ms. Loewen has nothing to disclose.Conflict of interest: Mr. Monchka has nothing to disclose.Conflict of interest: Dr. Mahmud reports grants from GlaxoSmithKline, grants from Sanofi Pasteur, grants from Pfizer, grants from Merck, grants from Roche, outside the submitted work; .Conflict of interest: Dr. Azad reports grants from Heart and Stroke Foundation of Canada/Canadian Lung Association / Canadian Respiratory Research Network / Allergy, Genes and Environment Network of Centres of Excellence (co-funders), grants from Children's Hospital Foundation of Manitoba, during the conduct of the study.Conflict of interest: No conflicts of interest %U https://erj.ersjournals.com/content/erj/early/2018/04/12/13993003.02070-2017.full.pdf