Impact of postpartum hospital length of stay on infant gut microbiota: a comprehensive analysis of vaginal and caesarean birth

Background: The primary concern with prolonged hospitalization following birth is the risk of acquiring hospital-acquired infections (HAIs) caused by opportunistic bacteria, which can alter the early establishment of gut microbiota.

Objective: To assess the association between postpartum hospital length of stay (LOS) and the composition of gut microbiota at 3 and 12 months of age according to birth mode.

Methods: In total, 1313 Canadian infants from the CHILD Cohort Study were involved in this study. Prolonged LOS was defined as ≥2 days following vaginal delivery (VD) and ≥3 days following caesarean section (CS). The gut microbiota of infants was characterized by Illumina 16S rRNA sequencing of faecal samples at 3-4 months and 12 months of age.

Findings: Following prolonged LOS, VD infants with no exposure to intrapartum antibiotics had a higher abundance of bacteria known to cause HAIs in their gut, including Enterococcus spp. at 3 and 12 months, Citrobacter spp. at 3 months, and Clostridioides difficile at 12 months. Abundance of Enterococcus spp. or Citrobacter spp. at 3 months significantly mediated the association between LOS and low abundance of Bacteroidaceae, or higher Enterococcaeae/Bacteriodaceae or Enterobacterales/Bacteroidaceae abundance ratios at 12 months of age in VD infants without intrapartum antibiotic exposure. HAI-causing Enterobacterales were also more abundant in later infancy in infants with prolonged LOS following CS. In the absence of exclusive breastfeeding at 3 months or any breastfeeding at 12 months, Porphyromonadaceae (of Bacteroidota) were depleted in CS infants with prolonged LOS.

Conclusions: Prolonged hospital stay after birth is associated with infant gut dysbiosis.