Cesarean delivery not associated with obesity in offspring

Within families, cesarean section is not associated with an increase in body mass index (BMI) z-score at 5 years of age, according to a new retrospective cohort study published in the journal JAMA Pediatrics.

Sheryl L. Rifas-Shiman, Department of Population Medicine, Harvard Medical School, Boston, Massachusetts, and colleagues conducted the study to determine whether there is an association between mode of delivery and BMI of offspring.

Cesarean delivery rates remain high and variable across hospitals, regions, and countries. Cesarean delivery may be a risk factor for childhood obesity, possibly because delivery route can influence the intestinal microbiomes, which may influence energy regulation. Previous meta-analyses have suggested that cesarean section is associated with increased risk of obesity in the offspring.

For the study, the researchers used data from Linked CENTURY (Collecting Electronic Nutrition Trajectory Data Using Records of Youth) study. 16140 siblings born between 1987 and 2003 and their 8070 mothers were included in the study. The delivery route, which was the main exposure, was obtained from birth certificates. The primary outcomes were age-specific and sex-specific BMI z-score (also called standard deviation score) at 5 years of age. BMI z-scores are measures of relative weight adjusted for child age and sex, for example, 0.0 would represent 50^th percentile BMI while 2.5 would be >99^th percentile.

Key Findings:

• 16,140 siblings were included from 8070 mothers
  
  
  
  • 19.9% of children had cesarean delivery
  
  
  • Mean (SD) BMI z-score at 5 years of age was 0.48 (1.00)
  
  
  
  


• Mean BMI z-score was
  
  
  
  • 0.45 among siblings who both had vaginal delivery
  
  
  • 0.51 among siblings with 1 cesarean and 1 vaginal delivery
  
  
  • 0.63 among siblings who both had cesarean delivery
  
  
  
  


• In the co-variate adjusted model, the within-family association of cesarean vs vaginal delivery was not significant
  
  
  
  • 0.04 higher BMI z-score at 5 years of age (95% CI, −0.04 to 0.11)
  
  
  
  


• The addition of the between-family consideration changed the association to 0.13 (95% CI, 0.04 to 0.22)


• In a model adjusted for the same covariates, but without decomposing the within-family and between-family effects, children with cesarean delivery had 0.13 higher BMI z score (95% CI, 0.08 to 0.17).

"Within families, cesarean section was not associated with an increase in BMI z-score at 5 years of age. Previous studies, which found the association with obesity and increased weight was limited by confounding," concluded the authors.

For further reference log on to 10.1001/jamapediatrics.2018.0674