In this longitudinal cohort study, the Chinese researchers investigated the impact of delivery mode and feeding pattern on the dynamics of the infant’s gut microbiota from 6 weeks to 6 months after delivery. They also investigated the correlation between the infant’s susceptibility to respiratory infections and changes in the gut microbiota caused by mode of delivery and feeding pattern. The results showed that exclusive breastfeeding restores perturbation in the infant’s gut microbiota caused by the mode of delivery (Cesarean section), and reduces susceptibility to respiratory infections in the first months of the infant’s life.
Numerous perinatal factors influence the maturation of gut microbiota, including delivery mode, feeding pattern, antibiotic exposure, and gestational age. The authors stated that recent studies have demonstrated that delivery mode is a major determinant of the gut microbiota during the first weeks of life. The natural transmission of the gut microbiota from mothers to offspring is disrupted by Cesarean section delivery. The lack of specific bacterial taxa in infants delivered by Cesarean section disturbs the maturation of the infant intestine and immune systems. The decrease in the health-promoting Bifidobacterium and the rise in potentially pathogenic Enterococcus, Staphylococcus, Streptococcus, and Klebsiella in infants delivered by Cesarean section have been associated with higher incidence of respiratory infections during the first year of life. This suggests that alterations in the gut microbiota may have a role in disease susceptibility induced by Cesarean delivery. On the other hand, the enrichment of Bifidobacterium, Escherichia, Bacteroides, and Parabacteroides in vaginally delivered infants can promote the utilization of human milk oligosaccharides and immune stimulation in early life. The effect of the delivery mode gradually decreases by 6 months of life or earlier, which suggests that the gut microbiota could recover after the Cesarean section delivery.
Additionally, the gut microbiota of exclusively breastfed and formula-fed infants are distinct, even when specific components are added to the formula to promote breastfed-like microbial communities. This demonstrates that the nutritional and immune benefits of breastfeeding are indispensable.
About the study
The study included 139 infants at 6 weeks postpartum, of whom 73% (101/139) completed the 6-month follow-up. Stool samples were collected from each infant at 6 weeks postpartum (n= 139) and 6 months postpartum (n= 101). The prenatal and perinatal information was obtained from electronic medical records and questionnaire surveys, including maternal age, gravidity, pre-pregnancy body mass index, delivery mode, gestational age, infant sex, birth weight, feeding pattern, and the occurrence of respiratory infections during the first 6 months of age.
The feeding pattern was divided into two types: the exclusive breastfeeding, defined as feeding with breast milk exclusively after birth, and mixed feeding, defined as feeding with a mixture of breast milk and formula milk in varying proportions. Respiratory infection events are defined as the occurrence of the following mother-reported symptoms: pneumonia, bronchitis, and fever (higher than 38 °C) accompanied by snuffling, sneezing, coughing, or wheezing.
Out of 139 infants, 93 infants (67%) were born by vaginal delivery, and 46 infants were born by Cesarean section delivery. Out of 101 infants, 71 infants (70%) were born by vaginal delivery, and 30 infants were born by Cesarean section delivery. The clinical variables were similar between the vaginally delivered and Cesarean section-delivered groups, except for gestational age, which was related to the delivery mode.
The researchers first conducted a chronological comparison of gut microbiota composition and community structure, which revealed markedly distinct infant’s gut microbiota between 6 weeks and 6 months of age. The infant’s gut microbiota shared a more homogeneous microbial community cluster at 6 months compared to 6 weeks. Clostridium sensu stricto1, Klebsiella, and Streptococcus, which are all found in the hospital environment, had higher relative abundances at 6 weeks. In contrast, Bifidobacterium, Bacteroides, Escherichia-Shigella, and Veillonella were enriched at 6 months of age.
The impact of delivery mode on the infant’s gut microbiota was then investigated. At 6 weeks postpartum, the composition and structure of the gut microbiota of infants delivered by Cesarean section differed from those of vaginally delivered infants, thereby confirming that the mode of delivery is a major determinant of differences in the gut microbiota during an early life. However, this difference disappeared at 6 months, indicating that changes in the gut microbiota related to the delivery mode diminish gradually throughout infancy.
The authors then hypothesized that the impact of delivery mode on the infant’s gut microbiota is affected by the feeding pattern. At 6 months postpartum, 101 infants were divided into two groups based on feeding pattern: exclusive breastfeeding and mixed feeding groups. Their stool samples were analyzed. In the mixed feeding group, there was a significant difference in the gut microbiota structure between vaginally delivered and Cesarean section-delivered infants. But, in the exclusive breastfeeding group, there was no significant difference in the gut microbiota structure between vaginally delivered and Cesarean section-delivered infants. These outcomes suggest that a disturbance in the gut microbiota observed in infants delivered by Cesarean section was mitigated by exclusive breastfeeding.
Scientists then conducted a cross-sectional analysis to examine specific taxa associated with feeding patterns. They compared the average relative abundance of the top 10 genera between vaginally delivered and Cesarean section-delivered infants. At 6 weeks, all vaginally delivered infants were enriched in Bacteroides and Escherichia-Shigella, while Cesarean section-delivered infants were depleted of these two commensal genera and enriched in Klebsiella, Veillonella, and Enterococcus. At 6 months postpartum, the microbial shifts induced by the delivery mode were restored through exclusive breastfeeding, resulting in similar gut microbial profiles between infants who were vaginally delivered and Cesarean section-delivered infants who were exclusively breastfed. In the mixed-feeding group, the relative abundances of the aforementioned taxa remained distinct between infants who were vaginally delivered and those who were delivered via Cesarean section, with a lower relative abundance of Bacteroides and a higher abundance of Klebsiella, Veillonella, and Streptococcus in infants delivered by Cesarean section. Between vaginally delivered and Cesarean section-delivered infants, the relative abundances of Escherichia-Shigella were comparable.
The authors then examined the correlation between the mode of delivery and the occurrence of respiratory infections during the first 6 months of the infant’s life. The incidence of respiratory infections was significantly higher in infants delivered via Cesarean section (9/71) than in vaginally delivered infants (10/30). Furthermore, genera associated with vaginal delivery were enriched in healthy infants, whereas genera associated with Cesarean section delivery (low Escherichia-Shigella and high Klebsiella) were enriched in infants who suffered from respiratory infections. These findings show that changes in the infant’s gut microbiota induced by delivery mode were associated with the occurrence of respiratory infections.
This study has shown that the perturbation of the infant’s gut microbiota caused by Cesarean section was associated with higher risks of respiratory infection in the first months of life. Exclusive breastfeeding mitigated these delivery mode-induced changes in the infant’s gut microbiota, resulting in decreased susceptibility to respiratory infections.
This article was published in Frontiers in Microbiology.
Liu Y, et al. A health-promoting role of exclusive breastfeeding on infants through restoring delivery mode-induced gut microbiota perturbations. Front. Microbiol. 2023; 14:1163269. (Open Access) https://www.frontiersin.org/articles/10.3389/fmicb.2023.1163269