Fathers Are a Source of Baby Gut Bacteria Too: After 1 Year, Their Contribution Matches Mothers'

A newborn's gut microbes come mainly from the mother, and cesarean delivery or antibiotics given during labor partly interrupt this transfer. Researchers at the University of Trento in Italy and the University of Helsinki in Finland reported in Cell Host & Microbe what they found when they looked at who fills the gap.

Strain-Level Tracking in Two Cohorts

The researchers analyzed two longitudinal metagenomic datasets. One was a cohort of 74 infants with 398 samples, and the other was 7 infants born by cesarean delivery who received a maternal fecal microbiota transplant (FMT), with 35 samples. The key was tracking who each microbe came from at the strain level rather than the species level, which distinguishes which family member passed on a strain even within the same species.

The results showed that fathers were a stable, steady source of strains regardless of delivery mode, and their cumulative contribution reached a level similar to the mothers' after one year. When maternal FMT was given to cesarean-born infants, strain sharing between mother and baby increased, the average growth rate of the bacteria that settled rose, and colonization by pathogenic bacteria decreased.

Limits

Because this is an analysis of observational cohorts, causation cannot be established, and the number of infants who received FMT is very small at 7. FMT is a treatment in a research setting and is not a general recommendation.