Breast Milk Microbiota Is Shaped by Mode of Delivery and Intrapartum Antibiotic Exposure

ABSTRACT The mode of delivery has been suggested to modulate the bacterial composition of breast milk but the impact of intrapartum antibiotic use on the milk microbiota is currently not known. The aim of this study was to dissect the effects of the mode of the delivery and intrapartum antibiotic administration on the microbial composition of breast milk. Breast milk samples were collected from 84 healthy mothers 1 month after the delivery. In all, 61 mothers had delivered vaginally and 23 of them had received intrapartum antibiotics, 13 women had delivered with non-elective caesarean section and 7 of them had received antibiotics, and 10 mothers had delivered with elective caesarean section without intrapartum antibiotic treatment. Both mode of delivery and intrapartum antibiotic exposure were significantly associated with changes in the milk microbial composition as assessed by analysis of similarities (ANOSIM) test (p=0.001). The mode of delivery had a more profound effect on the milk microbiota composition as compared to intrapartum antibiotic exposure. Although the clinical significance of breast milk microbiota is currently poorly understood, this study shows that caesarean section delivery has an independent effect on breast milk microbiota composition. The dysbiosis observed in infants born by caesarean section delivery may be aggravated by the aberrant breast milk microbiota.