A Casual Mechanism that Associates Cesarean Born Kids with Obesity

A new study published in the Science Advances journal has found a casual mechanism that explains why cesarean deliveries are likely to result in obesity in the progenies.

Introduction
Cesarean deliveries are often performed to save the life of the mother or the baby. These may also be recommended for other medical reasons. Sometimes, the mothers go for an elective surgery. So, there has been a worldwide increase in cesarean surgeries by 50%. In the U.S, 32.5%, that is, about a third, of all live births are via cesarean surgeries.

A team of scientists from the New York University (NYU) School of Medicine in New York City began to analyze the association between a cesarean delivery and the offspring’s weight. The research headed by a microbiologist- Dr. Maria Dominguez-Bello, who works at the NYU’s Sackler Institute, builds on previous works which have demonstrated an association between cesarean delivery and the likelihood of obesity in children. A study has reported that there is a 15% likelihood for children born through cesarean to become obese, and this higher risk is irrespective of the weight of the mother.

Various studies that have tried to explain this association have been merely observational. But the current study explains a casual mechanism. It explains that cesarean delivery hinders the natural transmission of microbes from the mother via her vaginal flora. For, it is this baby’s founding microbiome that informs the infant’s metabolic and immune systems, and makes them ready for a healthy adulthood.

This research which was carried out on mice, is the pioneer study to demonstrate a causal association between cesarean delivery and obesity in mammals, says Dr. Dominguez-Bello.

The study
For the study, 34 mice were delivered through cesarean surgeries and compared with 35 mice which were born through the natural mode. To analyze the effect of the delivery mode on the microbiome of the mice, the scientists extracted and studied the DNA of the bacteria in the progeny.

They discovered significant difference in the microbiomes of the normally-delivered mice and in cesarean-born mice. The normally delivered ones had bacteria like Ruminococacea, Clostridiales, and Bacteroides – which previous studies have linked with a thinner type of body. The researchers also tracked the changes in bacteria as those mice development into adulthood. Further, the bacterial composition of normal delivery mice normally matured into adulthood, but that of the cesarean delivered ones did not.

The researchers found that the microbiome in the cesarean delivered mice initially matured rapidly but then became static. They observed that females exhibited significant differences owing to delivery mode than males. They put is as “mice gained 33 [percent] more weight at age 15 weeks if they were born by [cesarean delivery] and for females it was 70 percent”.

Conclusion
The study supports the hypothesis that normal metabolic and immune development in mammals requires the acquiring of maternal vaginal microbes. Further research is needed to determine whether obesity can be prevented by the dominance of certain bacterial groups. If this is confirmed, new ways have to be developed to restore the natural mix of bacteria in the newborns. Another study has been performed by the same team to demonstrate how beneficial bacteria can be replenished in new C-section borns by swabbing them with their mother’s birth fluid.

This is a very urgent issue to be addressed as now-a-days many moms worldwide opt for a cesarean surgery. Dr. Dominguez-Bello said that research needs to be directed in isolating those microbes that are responsible for increased obesity and those that are anti-obesogenic.

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