In the United States, the cesarean birth rate rose from 20.7 percent in 1996 to 32 percent in 2007.1 The increase is thought to be due to the increase in maternal request of cesarean birth2—that is, the request by the pregnant women without medical necessity.

In a recent study published in Archives of Diseases in Childhood involving over 1200 children born to women between 1999 and 2002, those children born by cesarean were found to have higher BMI (body mass index, a measure of obesity) and higher subcutaneous body fat at age 3 when compared to those children born vaginally.3 Cesarean delivery has previously been found to be a risk factor for the development of childhood asthma and allergies. Brenda recently blogged about the connection between cesarean delivery and asthma.

The researchers suggested that, “the composition of intestinal microbiota acquired at birth among cesarean and vaginally delivered newborns may contribute to their risk of obesity by age 3.” Studies have found differences in the intestinal bacteria of cesarean born versus vaginally born children.4,5 Most studies have found that infants born by cesarean have higher amounts of the Firmicutes bacteria, and lower amounts of Bacteroidetes.3

This same gut microbial profile—higher Firmicutes and lower Bacteroidetes—has been found in obese individuals, as well.6 Further, studies have found that weight loss is associated with a lowering of Firmicutes levels and/or an increase of Bacteroidetes.6,7 Other studies have found that children who were overweight at ages 7–10 had lower amounts of bifidobacteria during infancy.8,9 Bifidobacteria are abundant in the intestines of healthy infants, and persist in a healthy digestive tract until after middle age.10

Two reasons for the change in intestinal microbiota seen in infants delivered by C-section include the addition of antibiotics during cesarean to reduce chances of infection, and the fact that the infants do not pass through the microbe-rich vagina, missing out on the inoculation of healthy bacteria from the mother. These are likely explanations for the difference in bacterial composition that we see may even lead to the development of obesity later in life.

Cesarean delivery is sometimes medically necessary; there is no doubt about that. But opting for cesarean birth when it is not medically necessary may not be the best option for supporting optimal health in the infant. In any case, I think it is a good idea for all mothers to take pre- and probiotics during pregnancy, and while breast feeding (especially after a C-section). Furthermore, adding probiotics to expressed breast milk or formula will ensure the baby has a chance to develop a healthy, balanced microbiome.  A healthy microbiome leads to a healthy balanced immune system, and balanced immunity may prevent type 1 autoimmune diabetes, asthma, obesity, and other autoimmune conditions of childhood, and their life-long effects.



  1. F. Menacker and B.E. Hamilton, “Recent trends in cesarean delivery in the United States.” NCHS Data Brief. 2010 Mar;(35):1–8.
  2. NIH State-of-the-Science Conference Statemnt on cesarean delivery on maternal rewuest. NIH Consens State Sci Statements. 2006;23:1–29.
  3. S.Y. Huh, et al., “Delivery by caesarean section and risk of obesity in preschool age children: a prospective cohort study.” Arch Dis Child. 2012 May 23. [Epub ahead of print]
  4. M.M. Gronlund, et al., “Fecal microflora in healthy infants born by different methods of delivery: permanent changes in intestinal flora after cesarean delivery.” J Pediatr Gastroenterol Nutr. 1999 Jan;28(1):19–25.
  5. S. Salminen, et al., “Influence of mode of delivery on gut microbiota composition in seven year old children.” Gut. 2004 Sep;53(9):1388–9.
  6. R.E. Ley, et al., “Microbial ecology: human gut microbes associated with obesity.” Nature. 2006 Dec 21;444(7122):1022–3.
  7. I. Nadal, et al., “Shifts in clostridia, bacteroides and immunoglobulin-coating fecal bacteria associated with weight loss in obese adolescents.” Int J Obes (Lond). 2009 Jul;33(7):758–67.
  8. M. Kalliomaki, et al., “Early differences in fecal microbiota composition in children may predict overweight.” Am J Clin Nutr. 2008 Mar;87(3):534–8.
  9. R. Luoto, et al., “Initial dietary and microbiological environments deviate in normal-weight compared to overweight children at 10 years of age.” J Pediatr Gastroenterol Nutr. 2011 Jan;52(1):90-5.
  10. T. Mitsuoka, “Bifidobacteria and their role in human health.” J Indus Microbiol Biotech. 1990;6(4):263–7.