Human Milk Feeding Patterns at 6 Months of Age are a Major Determinant of Fecal Bacterial Diversity in Infants

Background Maternal pre-pregnancy obesity and human milk feeding have been associated with altered infant gut microbiota. Research aim Determine the relationships between maternal pre-pregnancy BMI, human milk exposure, and their influence on the infant microbiota simultaneously. Methods This was a cross-sectional study of infants at 6 months of age (N= 36), a time when many infants are fed a mixed diet of human milk and other foods. Fecal samples and participant information were collected from a subset of dyads enrolled in two related prospective cohorts (ARCH(GUT)and BABY(GUT)) in Michigan. Sequencing the V4 region of the 16S gene was used to analyze fecal bacterial samples collected from 6-month-old infants. Participants were grouped into four categories designated by their extent of human milk exposure (100%, 80%, 50%-80%, <= 20% human milk in the infant diet) and by maternal pre-pregnancy BMI category (normal, overweight, obese). Results Fewer participants with pre-pregnancy obesity were breastfeeding at 6 months postpartum compared to non-obese participants (35.7% and 81.8%, respectively). In univariate analyses, maternal pre-pregnancy BMI and human milk exposure were both significantly associated with alpha and beta diversity of the infant microbiota. However, in multivariate analyses, human milk exposure accounted for 20% of the variation in alpha diversity, but pre-pregnancy BMI was not significantly associated with any form of microbiota diversity. Conclusions The proportion of the infant diet that was human milk at 6 months was the major determinant of alpha and beta diversity of the infant. Maternal obesity contributes to the gut microbiota by its association with the extent of human milk feeding.

Automated summary

This study found that maternal pre-pregnancy BMI and human milk exposure influenced the alpha and beta diversity of the infant gut microbiota at 6 months of age. The major determinant was the proportion of human milk in the infant diet.