Breast Milk Mitigates Microbial Differences Caused by Varying Modes of Infant Delivery Despite the C-section Microbiome Displaying an Increased Resistance to Change Over a Naturally Delivered Microbiome

Abstract

Early life infancy is a crucial period for shaping the microbiota, as many factors during this period are responsible for driving the assembly of the infant microbiome. Two of the most studied early-life habits and practices that have drastic impacts on the infant microbiome are the mode of infant delivery and diet. Over the years, caesarean section (C-section) delivery rates have been on the rise globally. Although microbial differences resulting from the mode of delivery become less striking later on in life, the microbiomes of C-section infants have notable differences in composition and diversity compared to those born vaginally. Our study established feed as having a stronger influence on the microbiota compared to mode of delivery. Accordingly, breast milk, to an extent, was able to mitigate differences caused by delivery, such that C-section infants supplemented with breast milk had a more similar profile to those born vaginally when compared to those fed formula. Breast milk stood out as a rare exception in its ability to modify the C-section microbiome. This is owing to the fact that the dysbiotic state commonly linked with C-section deliveries, typically displays a degree of resistance to changes induced by external factors (21, 4). This finding is clinically significant as C-section deliveries have been consistently correlated with an increased chance of developing autoimmune disorders, and breast milk being able to modify the C-section microbiome so that it more closely resembles the healthier vaginal state can be considered a therapeutic intervention. This study highlights the importance of diet as a major factor influencing the infant microbiome and establishes breast milk as the preferred feed over formula for C-sectionally delivered infants.