Background It has been suggested that aberrant microbiota development may predispose to some diseases (eg, allergic disorders, obesity, inflammatory bowel disease). Thus, the establishment and composition of the gut microbiota is important. In early infancy, a number of factors are considered to affect the colonisation pattern, including maternal education, diet, probiotic use and antibiotic use; delivery and birth characteristics; type of infant feeding; antibiotic/antimycotic agents used during early life and the home environment (siblings, living on a farm, furry pets). The rate of Caesarean sections is now increasing both in developed and some developing countries, which may have an impact on intestinal microbiota (total amount and type of microbial species present in the gastrointestinal tract).
Objective To evaluate systematically and update data on the effects of mode of delivery on gut microbiota.
Methods The MEDLINE databases were searched in June 2008; additional references were obtained from reviewed articles. Only trials evaluating the effect of the mode of delivery (natural delivery vs Caesarean section delivery) on gut microbiota of term infants and published in the last 10 years were considered for inclusion. Special emphasis was given to studies using molecular approaches, as many bacterial species cannot be cultured using traditional culture techniques.
Results Four trials were included. The first study (Gronlund et al. J Pediatr Gastroenterol Nutr 1999), which cultured fecal flora on selective and non-selective media, demonstrated that the fecal colonisation of 64 healthy infants born by Caesarean delivery to mothers who received antibiotic prophylaxis administered before delivery was delayed. Bifidobacterium-like bacteria and Lactobacillus-like bacteria colonisation rates reached the rates of vaginally delivered infants at 1 month and 10 days, respectively. Compared with vaginally delivered infants, those born by Caesarean section were significantly less often colonised with bacteria of the Bacteroides fragilis group. This study also showed that the disturbances of the intestinal microbiota may be present up to 6 months of age. The second trial involving 60 children demonstrated the influence of mode of delivery on gut microbiota composition beyond infancy (Salminen et al. Gut 2004). In children 7 years of age, a fluorescent in-situ hybridisation method showed a significantly higher number of Clostridia in children delivered vaginally compared with those born by Caesarean section. No differences were observed in other fecal bacteria or total numbers of bacteria. The third study was carried out in 1032 infants at 1 month of age by Dutch investigators (Penders et al. Pediatrics 2006). Their analysis of gut microbiota by quantitative real-time PCR showed that in comparison with vaginal delivery at home, Caesarean section resulted in lower colonisation rates and counts of bifidobacteria and B fragilis-group species, whereas the prevalence and counts of Clostridium difficile and counts of Escherichia coli were higher. The fourth study, which used fluorescence in-situ hybridisation, demonstrated that infants (n = 165) delivered by Caesarean section have fewer bifidobacteria at an early age (Huurre et al. Neonatology 2008).
Conclusions Recent studies confirm different colonisation patterns in infants born by vaginal or Caesarean delivery, which may persist beyond infancy. The exact effects of those differences on children’s health are unclear but potentially may increase the risk of specific diseases.