• Allergy;
  • antibiotics;
  • immunology;
  • intestinal flora

Antibiotics are increasingly prescribed in the peripartum period, for both maternal and fetal indications. Their effective use undoubtedly reduces the incidence of specific invasive infections in the newborn, such as group B streptococcal septicaemia. However, the total burden of infectious neonatal disease may not be reduced, particularly if broad-spectrum agents are used, as the pattern of infections has been shown to alter to allow dominance of previously uncommon organisms. This area has been relatively understudied, and there are almost no studies of long-term outcome. Recent findings suggest that such long-term data should be sought. First, there is evidence that organisms initially colonising the gut at birth may establish chronic persistence in many children, in contrast to prompt clearance if first encountered in later infancy, childhood or adulthood. Second, there is a rapidly advancing basic scientific data showing that individual members of the gut flora specifically induce gene activation within the host, modulating mucosal and systemic immune function and having an additional impact on metabolic programming. We thus review the published data on the impact of perinatal antibiotic regimens upon composition of the flora and later health outcomes in young children and summarise the recent scientific findings on the potential importance of gut flora composition on immune tolerance and metabolism.