Childhood obesity risk linked to delivery method

By Ingrid Grasmo

Delivery by cesarean section may double the risk for childhood obesity compared with vaginal delivery, show US study findings.

"Expectant mothers choosing caesarean delivery in the absence of a medical indication should be aware that their children may have a higher risk of obesity," say Susanna Huh (Children's Hospital Boston, Massachusetts) and colleagues.

For the study, the researchers followed up 1255 mother and child pairs who attended eight outpatient maternity services in eastern Massachusetts between 1999 and 2002. All women joined the study before 22 weeks' gestation.

Body composition of all children was measured at 3 years of age, including body mass index (BMI), obesity, and sum of triceps plus subcapsular skinfold thicknesses (SS+TR).

In total, 284 (22.6%) children were delivered by cesarean section. Average maternal BMI was significantly higher among infants delivered by cesarean section compared with vaginal delivery (25.8 vs 24.3 kg/m²), and breastfeeding duration was shorter for infants delivered by cesarean section (5.6 vs 6.7 months).

After adjusting for maternal age, education, race/ethnicity, child age and gender, pre-pregnancy BMI, and birthweight, the researchers found that 15.7% of children delivered by caesarean section were obese compared with 7.5% of children born by vaginal delivery at 3 years of age (odds ratio [OR]=2.10).

Cesarean delivery was also associated with a 0.20 unit increment in age 3 BMI z-score and with a 0.94 mm increment in the sum of skinfolds.

Each increment in maternal BMI was associated with an increased risk for the child being overweight or obese (OR=1.04 and 1.10 per kg, respectively), as was birthweight (OR 1.96 and 2.02 per kg).

Previous research has shown that children born by cesarean section have higher numbers of Firmicutes bacteria, and lower numbers of Bacterioides bacteria in the gut, the team notes.

The researchers suggest that gut bacterial composition could influence the development of obesity by increasing energy extraction from the diet, and by stimulating cells to boost insulin resistance, inflammation, and fat deposits.

Writing in the Archives of Disease in Childhood, they conclude: "Further studies are needed to confirm our findings and to explore mechanisms underlying this association."

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