Review ArticleFactors Influencing the Intestinal Microbiome During the First Year of LifeZimmermann, Petra MD*,†,‡,§; Curtis, Nigel FRCPCH, PhD*,†,‡Author Information From the *Department of Paediatrics, The University of Melbourne, Parkville, Australia †Infectious Diseases Unit, The Royal Children’s Hospital Melbourne, Parkville, Australia ‡Infectious Diseases & Microbiology Research Group, Murdoch Children’s Research Institute, Parkville, Australia §Infectious Diseases Unit, University of Basel Children’s Hospital, Basel, Switzerland. Accepted for publication April 19, 2018. The authors have no funding or conflicts of interest to disclose. P.Z. drafted the initial manuscript. N.C. critically reviewed and revised the manuscript. Both authors approved the final article as submitted. Address for correspondence: Petra Zimmermann, MD, Department of Paediatrics, The University of Melbourne, Royal Children’s Hospital Melbourne, Parkville, VIC 3052, Australia. E-mail: firstname.lastname@example.org The Pediatric Infectious Disease Journal: December 2018 - Volume 37 - Issue 12 - p e315-e335 doi: 10.1097/INF.0000000000002103 Buy Metrics Abstract The intestinal microbiome plays a crucial role in the development of the immune system and regulation of immune responses. Many factors influence the composition of the infant intestinal microbiome and therefore the development and function of the immune system. This, in turn, may alter the risk of subsequent allergies, autoimmune diseases and other adverse health outcomes. Here, we review factors that influence the composition of the intestinal microbiome during the first year of life, including birth location, gestational age, delivery mode, feeding method, hospitalization, antibiotic or probiotic intake and living conditions. Understanding how the early intestinal microbiome is established and how this is perturbed provides many opportunities for interventions to improve health. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.