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 analyze 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 total, 61 mothers had delivered vaginally, 23 of which had received intrapartum antibiotics, 13 women had delivered with non-elective cesarean section, 7 of which had received antibiotics, and 10 mothers had delivered with elective cesarean 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 cesarean section delivery has an independent effect on breast milk microbiota composition. The dysbiosis observed in infants born by cesarean section delivery may be aggravated by the aberrant breast milk microbiota.

Keywords: breast milk; cesarean section; intrapartum antibiotics; microbiota composition; non-communicable diseases.

Figure 1

Breast milk microbiota composition 1 month after delivery in mothers who delivered vaginally (VD) or by cesarean section (CS) and exposed or not exposed to intrapartum antibiotics (IAB). The relative abundance of phyla (A) and the 15 most abundant families (B) are presented.

Figure 2

Significant differences in breast milk microbiota composition were detected 1 month after delivery between mothers who delivered vaginally (VD) or by cesarean section (CS) and exposed or not exposed to intrapartum antibiotics (IAB) by Bray-Curtis Principal coordinate analysis (PCoA) and ANOSIM test; p = 0.001 (A). When the mothers were grouped by only mode of delivery, VD mothers clustered distinctly from CS mothers; ANOSIM p = 0.001 (B). In contrast, no significant clustering was detected when the mothers were group by IAB; ANOSIM p = 0.54 (C).

Figure 3

Significant differences in breast milk microbiota diversity as assessed by Shannon index were observed 1 month after delivery between mothers who delivered vaginally (VD) or by cesarean section (CS) and exposed or not exposed to intrapartum antibiotics (IAB) (A). VD mothers exhibited significantly higher breast milk microbiota diversity as compared to CS mothers (B) while IAB was associated with higher microbiota diversity in breast milk (C). In a similar fashion, breast milk microbiota richness varied significantly depending on birth mode and IAB (D). Breast milk microbiota richness was significantly higher in VD mothers compared to CS mothers (E). IAB was associated with increased breast milk microbiota richness (F).

Figure 4

Venn diagram presenting shared bacterial families in breast milk microbiota in mothers who delivered vaginally (VD) or by cesarean section (CS) and exposed or not exposed to intrapartum antibiotics (IAB).