title: Antibiotic Exposure During the First 6 Months of Life and Weight Gain During Childhood.
abstract: OBJECTIVE
  Early-life antibiotic exposure has been associated with increased adiposity in animal models, mediated through the gut microbiome. Infant antibiotic exposure is common and often inappropriate. Studies of the association between infant antibiotics and childhood weight gain have reported inconsistent results.
  
  
  OBJECTIVE
  To assess the association between early-life antibiotic exposure and childhood weight gain.
  
  
  METHODS
  Retrospective, longitudinal study of singleton births and matched longitudinal study of twin pairs conducted in a network of 30 pediatric primary care practices serving more than 200,000 children of diverse racial and socioeconomic backgrounds across Pennsylvania, New Jersey, and Delaware.
  
  
  METHODS
  Children born between November 1, 2001, and December 31, 2011, at 35 weeks' gestational age or older, with birth weight of 2000 g or more and in the fifth percentile or higher for gestational age, and who had a preventive health visit within 14 days of life and at least 2 additional visits in the first year of life. Children with complex chronic conditions and those who received long-term antibiotics or multiple systemic corticosteroid prescriptions were excluded. We included 38,522 singleton children and 92 twins (46 matched pairs) discordant in antibiotic exposure. Final date of follow-up was December 31, 2012.
  
  
  METHODS
  Systemic antibiotic use in the first 6 months of life.
  
  
  METHODS
  Weight, measured at preventive health visits from age 6 months through 7 years.
  
  
  RESULTS
  Of 38,522 singleton children (50% female; mean birth weight, 3.4 kg), 5287 (14%) were exposed to antibiotics during the first 6 months of life (at a mean age of 4.3 months). Antibiotic exposure was not significantly associated with rate of weight change (0.7%; 95% CI, -0.1% to 1.5%; P = .07, equivalent to approximately 0.05 kg; 95% CI, -0.004 to 0.11 kg of added weight gain between age 2 years and 5 years). Among 92 twins (38% female; mean birth weight, 2.8 kg), the 46 twins who were exposed to antibiotics during the first 6 months of life received them at a mean age of 4.5 months. Antibiotic exposure was not significantly associated with a weight difference (-0.09 kg; 95% CI, -0.26 to 0.08 kg; P = .30).
  
  
  CONCLUSIONS
  Exposure to antibiotics within the first 6 months of life compared with no exposure was not associated with a statistically significant difference in weight gain through age 7 years. There are many reasons to limit antibiotic exposure in young, healthy children, but weight gain is likely not one of them.
authors.affiliation: Center for Pediatric Clinical Effectiveness, Division of Infectious Diseases, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania2Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Gerber
authors.affiliation: Division of Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Bryan
authors.affiliation: Center for Pediatric Clinical Effectiveness, Division of Infectious Diseases, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Rachael K
authors.initials: RK
authors.lastname: Ross
authors.affiliation: Department of Pediatrics and Child Health, University of Manitoba, and Children's Hospital Research Institute of Manitoba, Winnipeg, Canada.
authors.forename: Carrie
authors.initials: C
authors.lastname: Daymont
authors.affiliation: Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia5Division of Gastroenterology, Hepatology, and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Parks
authors.affiliation: Division of Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
authors.forename: A Russell
authors.initials: AR
authors.lastname: Localio
authors.affiliation: Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia6Department of Biomedical and Health Informatics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Grundmeier
authors.affiliation: Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia5Division of Gastroenterology, Hepatology, and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Virginia A
authors.initials: VA
authors.lastname: Stallings
authors.affiliation: Center for Pediatric Clinical Effectiveness, Division of Infectious Diseases, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania2Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
authors.forename: Theoklis E
authors.initials: TE
authors.lastname: Zaoutis
mesh_terms: D000367:Age Factors; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D001724:Birth Weight; D002648:Child; D002675:Child, Preschool; D003691:Delaware; D005260:Female; D005865:Gestational Age; D006128:Growth / Q000502:physiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D016555:Matched-Pair Analysis; D009515:New Jersey; D010414:Pennsylvania; D011322:Primary Prevention; D012189:Retrospective Studies; D014429:Twins, Dizygotic / Q000706:statistics & numerical data; D015430:Weight Gain / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents