As we have already explained in this blog, the way you are born might impact your health with life-long lasting effects. Epidemiological studies have shown there is a correlation between the increase of C-section in the world in the last decades and the rise of diseases such as allergies, celiac disease or obesity.

According to World Health Organisation (WHO), C-section is a life-saving practice needed in 10-15% of births to avoid risking the life of the mother or the child during childbirth. However, this surgical procedure is often overused in some regions of the world, where it is used in half the deliveries. As it is a medical intervention, antibiotics are given to prevent any possible infection.

The hypothesis is that both C-section and antibiotics together alter the natural transmission of microbiota from the mother to the child, and thus the ‘education’ these microorganisms provide to metabolic and immune systems early in development.

The study confirms the results of research by the NYU School of Medicine in humans, which concluded that cesarean deliveries reduced gut microbiota diversity

“The question whether a baby’s founding microbiota affects its future obesity risk becomes more urgent as C-sections are increasingly used by choice in many parts of the world”, says Maria Gloria Dominguez Bello, associate professor in the Department of Medicine at NYU School of Medicine.

To answer this question, Dominguez-Bello and colleagues did an experiment with mice, 34 delivered in the lab by C-section, without using antibiotics, and 35 delivered vaginally. They raised both groups of pups under the same condition and tracked their weight for 15 weeks after weaning. They observed that at that point, C-section mice had gained 33% more weight compared to vaginally born rodents.

And what was more intriguing and for what authors of the study have no explanation at all, female c-section born rodents gained more weight than their male counterparts.

Moreover, researchers used genomic techniques in order to determine the gut microbiota composition of the mice four weeks after weaning, when the animals were 8 weeks old. The analysis showed that the ones born naturally had a normal mixture of microorganisms, whereas those delivered by C-section lacked Bacteroides, Ruminococcaceae, Lachnospiraceae and Clostridiales, bacterial groups linked to lean body types.

“Our study is the first one to demonstrate a causal relationship between C-section and increased body weight in mammals”, says lead study author Domínguez-Bello.

The study, published in Science Advances, also confirms the findings of a recent NYU School of Medicine study in human babies that found that birth by C-section decreased the diversity of gut microbiota through the first year of life.

Despite their interesting results, it has to be taken with precaution. To start with it was conducted with animals, so the results cannot be directly extrapolated to humans, as we are far more complicated than mice.

To continue with, some studies, such as one led by Kjersti Maria Aagaard, who we have also interviewed in this blog, have already shown that there is no a long term impact of mode of delivery in human health.

The role of maternal breastfeeding in helping a healthy colonization of gut microbiota is known, but it was not investigated in this research, nor the use of antibiotics or whether those differences researchers saw in mice persist over the years. So be careful before blaming for your extra pounds your birthing!



Article reference

Martinez KA, Devlin JC, Lacher C et al. Increased weight gain by C-section: Functional significance of the primordial microbiome. Science Advances, 2017 DOI: 10.1126/sciadv.aao1874