The Effect of Intrapartum Antibiotic Prophylaxis at Caesarean Section on Childhood Obesity: A Quasi-Experimental Study in Two Bi-Ethnic UK Cohorts.

BACKGROUND

Clinical guidelines now recommend administering intrapartum antibiotic prophylaxis (IAP) before skin incision at caesarean section to prevent maternal infection. However, this practice exposes the fetus to antibiotics, raising concerns about potential long-term effects on the infant microbiome and the risk of childhood obesity.

OBJECTIVES

To assess whether the timing of IAP at caesarean section-before skin incision versus after umbilical cord clamping-is associated with childhood obesity at age 4-5 years.

METHODS

We conducted a quasi-experimental study of a hospital-wide policy change in clinical practice using data from two birth cohorts (Born in Bradford [BiB] and Born in Bradford's Better Start [BiBBS]). The study included 1985 children of White British or Pakistani heritage born by caesarean section between 2007 and 2019. Children exposed to pre-incision IAP (n = 324) were compared with those unexposed (post-cord clamping IAP; n = 1661). The primary outcome was obesity (BMI z-score > 95th percentile) at age 4-5 years. Adjusted Risk Ratios (aRR) were estimated using multivariable Poisson regression stratified by ethnicity.

RESULTS

The prevalence of obesity was 11.9%. Adjusted risk ratios for obesity were 1.25 (95% CI 0.53 to 2.98) for White British children and 1.25 (95% CI 0.64 to 2.43) for Pakistani children. Similarly, estimates for BMI z-score had wide confidence intervals indicating, limited precision.

CONCLUSIONS

We did not observe a clear difference in childhood obesity at 4-5 years between pre-incision and post-cord clamping prophylactic antibiotics at caesarean section. Confidence intervals were wide, and modest clinically relevant effects cannot be excluded. Findings are compatible with no large adverse effect and may provide reassurance regarding the metabolic safety of current clinical practice.