Association between mode of delivery and body mass index at 4-5 years in White British and Pakistani children: the Born in Bradford birth cohort.

Background: Globally, it is becoming more common for pregnant women to deliver by caesarean section (CS). In 2020, 31% of births in England were CS, surpassing the recommended prevalence of CS. Concerns have been raised regarding potential unknown consequences of this mode of delivery. Childhood adiposity is also an increasing concern. Previous research provides inconsistent conclusions on the association between CS and childhood adiposity. More studies are needed to investigate the consequences of CS in different populations and ethnicities. Therefore, this study investigates the association between mode of delivery and BMI, in children of 4-5 years and if this differs between White British (WB) and Pakistani ethnicities, in Bradford UK.

Methods: Data were obtained from the Born in Bradford (BiB) cohort, which recruited pregnant women at the Bradford Royal Infirmary, between 2007 and 2010. For these analyses, a sub-sample (n = 6410) of the BiB cohort (n = 13,858) was used. Linear regression models determined the association between mode of delivery (vaginal or CS) and BMI z-scores at 4-5 years. Children were categorised as underweight/healthy weight, overweight and obese, and logistic regression models determined the odds of adiposity. Effect modification by ethnicity was also explored.

Results: Multivariable analysis found no evidence for a difference in BMI z-score between children of CS and vaginal delivery (0.005 kg/m, 95% CI = - 0.062-0.072, p = 0.88). Neither was there evidence of CS affecting the odds of being overweight (OR = 1.05, 95% CI = 0.86-1.28, p = 0.65), or obese (OR = 0.98, 95% CI = 0.74-1.29, p = 0.87). There was no evidence that ethnicity was an effect modifier of these associations (p = 0.97).

Conclusion: Having CS, compared to a vaginal delivery, was not associated with greater adiposity in children of 4-5 years in this population. Concerns over CS increasing adiposity in children are not supported by the findings reported here using the BiB study population, of both WB and Pakistani families.