Race-specific Association of Caesarean-Section Delivery with Body Size at Age 2 Years.

OBJECTIVE: African American children are at higher risk of obesity than White children and African American women are more likely to undergo caesarean-section (CS) delivery than White women. CS is associated with childhood obesity; however, little is known whether this relationship varies by race. We examined if the association of CS with obesity at age 2 years varied by race. DESIGN: Longitudinal birth cohort. SETTING: Birth cohort conducted in a health care system in metropolitan Detroit, Michigan with follow-up at age 2 years. PARTICIPANTS: 639 birth cohort participants; 367 children (57.4%) were born to African American mothers and 230 (36.0%) children were born via CS. MAIN OUTCOME MEASURES: Obesity defined as body mass index ≥95th percentile at age 2 years. RESULTS: Slightly more children of African American (n=37; 10.1%) than non-African American mothers (n=18; 6.6%) were obese (P=.12). There was evidence of effect modification between race and delivery mode with obesity at age 2 years (interaction P=.020). In children of African American mothers, CS compared to vaginal birth was associated with a significantly higher odds of obesity (aOR=2.35 (95% CI: 1.16, 4.77), P=.017). In contrast, delivery mode was not associated with obesity at age 2 years in children of non-African American mothers (aOR=.47 (95% CI: .13, 1.71), P=.25). CONCLUSIONS: There is evidence for a race-specific effect of CS on obesity at age 2 years; potential underlying mechanisms may be racial differences in the developing gut microbiome or in epigenetic programming. Future research is needed to determine if this racial difference persists into later childhood.