Cesarean section and socioeconomic status are associated with Bifidobacterium abundance and intestinal physiology: observations from a cross-sectional study in formula-fed infants

Development of the gut microbiota in the first months of life is influenced by multiple environmental factors such as type of birth and diet which may have prolonged impact on growth and health. However, in developing countries such as Mexico, with high rates of cesarean deliveries, knowledge about gut microbiota development in early life stages are still limited. Through characterization, by 16S sequencing, of 307 formula-fed infants aged 1–4 months, we identified that abundance of key taxa was highly associated with birth mode and that socioeconomic status (evaluated as monthly family income) showed a modifying effect. Particularly, infants born by C-section and from families with a higher monthly income showed 57% lower Bifidobacterium abundance compared to those born vaginally and from families with a lower income. Additionally, these children exhibited higher fecal pH and lower fecal acetate. Interestingly, infants with a low weight-for-length z-score showed lower abundance of Bifidobacterium compared to those with an adequate z-score and a trend towards a higher fecal pH compared to those with an adequate z-score. This study supports that in the first months of life, C-section shape key taxa abundance, such as Bifidobacterium and that socioeconomic status show an important modifying effect. These changes are related to markers of intestinal physiology that shape gut maturation in early life and might be a determinant of current and future health.