May 24, 2012 — Caesarean delivery doubles the risk for childhood obesity, according to a prospective cohort study published online May 23 in the Archives of Disease in Childhood. The reason may be different intestinal bacteria than those acquired during vaginal birth.
Susanna Y. Huh, MD, MPH, from the Department of Pediatrics, Harvard Medical School, and Division of Gastroenterology and Nutrition, Children’s Hospital Boston, Massachusetts, and colleagues evaluated 1255 mother–child pairs attending 8 outpatient maternity practices in the Boston area between 1999 and 2002. The researchers weighed and measured children at birth, 6 months, and 3 years, adding triceps and subscapular skinfold thicknesses at the 3-year check. Mothers submitted questionnaires at 1 and 2 years postpartum.
Approximately one quarter of deliveries were surgical (22.6%; 284 children). These women weighed more than the women delivering vaginally; their babies weighed more, accounting for gestational age; and the mothers did not breast-feed for as long as the women who delivered vaginally.
Nearly 16% of children delivered surgically became obese compared with 7.5% of those born vaginally. Birth by caesarean delivery was associated with higher odds of obesity at age 3 years (odds ratio, 2.10, 95% confidence interval [CI], 1.36 - 3.23), higher mean body mass index z-score (0.20 units; 95% CI, 0.07 - 0.33), and higher skinfold thicknesses (0.94 mm; 95% CI, 0.36 - 1.51), with adjustments for birth weight, prepregnancy maternal body mass index, and other factors. The results are consistent with those of a smaller, retrospective study of 3- to 6-year-olds in China.
An explanation for the different risks for obesity with the 2 birth methods may lie in the microbiome, the communities of microorganisms that colonize the human gastrointestinal tract. Each method may introduce different bacterial species.
Gut bacteria affect the efficiency of energy extraction from nutrients and may stimulate cells to boost insulin resistance, inflammation, and fat deposits, the authors write. Specifically, higher numbers of Firmicutes and lower numbers of Bacteroides colonize the guts of children born by caesarean delivery. Other studies have shown this pattern in the gut microbiomes of obese individuals.
Limitations of the study include self-reporting of prepregnancy weight and the generalizability of the highly educated and earning study population to the general population.
The researchers suggest further studies to confirm the association between caesarean delivery and obesity and to further investigate the gut bacteria hypothesis. An alternative explanation may be effects of antibiotic prophylaxis given during caesarean delivery on intestinal bacteria.
The risk for obesity did not differ between planned and emergency caesarean deliveries, suggesting that bacteria acquired when membranes rupture are not a factor in elevated obesity risk, the researchers write.
One in 3 deliveries in the United States is surgical. Previous studies have associated caesarean delivery with increased risk for asthma and allergic rhinitis. "A mother who chooses caesarean delivery...should be aware of potential health risks to her and her baby, including childhood obesity," the researchers conclude.
The study was supported by grants from the National Institutes of Health. The authors have disclosed no relevant financial relationships.
Arch Dis Child. Published online May 23, 2012. Abstract
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