Supplementary information files for "Timing of intrapartum antibiotics at caesarean section and risk of asthma, eczema and allergic rhinitis: results from a natural experiment"

Supplementary files for article "Timing of intrapartum antibiotics at caesarean section and risk of asthma, eczema and allergic rhinitis: results from a natural experiment"<br><br><b>Objective:</b> To investigate whether the risk of asthma, eczema and allergic rhinitis at 5 years in children born by caesarean section (CS) differs by the timing of antibiotic administration to the mother (pre‐incision vs. post‐cord clamping).<br><b>Design:</b><b> </b>Natural experiment using birth cohort data.<b>Setting:</b> UK single centre population‐based birth cohort.<b>Participants:</b> 3013 liveborn children delivered by CS, from the Born in Bradford (BiB) cohort born 2007–2011 and BiB's Better Start (BiBBS) cohort born 2016–2019. Only the first‐born of multiple births was included.<b>Main Outcome Measures:</b> Risk of asthma, atopic eczema and allergic rhinitis at age 5 years.<b>Results:</b> Among 3013 children, 579 (19.2%) were exposed to pre‐incision antibiotics. At 5 years, 272 (9.0%) children had asthma, 672 (22.3%) had eczema and 180 (6.0%) had allergic rhinitis. There was no evidence of an increased risk of asthma (adjusted risk ratio [aRR] 1.01, 95% CI 0.56, 1.83; adjusted risk difference [aRD] 0.08 per 100, 95% CI −5.28, 5.44), eczema (aRR 0.96, 95% CI 0.68, 1.35; aRD −1.01 per 100, 95% CI −8.65, 6.63) or allergic rhinitis (aRR 1.16, 95% CI 0.59, 2.28; aRD 0.88 per 100, 95% CI −3.17, 4.92) at 5 years in children exposed to pre‐incision antibiotics versus post‐cord clamping.<b>Conclusions:</b> This study found no evidence of an association between pre‐incision antibiotics for CS and increased risk of asthma, eczema or allergic rhinitis by age 5. These findings contribute to the evidence base informing the optimum timing of maternal antibiotic prophylaxis for CS, balancing risks and benefits to the mother and her child.