title: Severe obesity, gestational weight gain, and adverse birth outcomes.
abstract: BACKGROUND
  The 2009 Institute of Medicine (IOM) Committee to Reevaluate Gestational Weight Gain Guidelines concluded that there were too few data to inform weight-gain guidelines by obesity severity. Therefore, the committee recommended a single range, 5-9 kg at term, for all obese women.
  
  
  OBJECTIVE
  We explored associations between gestational weight gain and small-for-gestational-age (SGA) births, large-for-gestational-age (LGA) births, spontaneous preterm births (sPTBs), and medically indicated preterm births (iPTBs) among obese women who were stratified by severity of obesity.
  
  
  METHODS
  We studied a cohort of singleton, live-born infants without congenital anomalies born to obesity class 1 (prepregnancy body mass index [BMI (in kg/m(2))]: 30-34.9; n = 3254), class 2 (BMI: 35-39.9; n = 1451), and class 3 (BMI: > or =40; n = 845) mothers. We defined the adequacy of gestational weight gain as the ratio of observed weight gain to IOM-recommended gestational weight gain.
  
  
  RESULTS
  The prevalence of excessive gestational weight gain declined, and weight loss increased, as obesity became more severe. Generally, weight loss was associated with an elevated risk of SGA, iPTB, and sPTB, and a high weight gain tended to increase the risk of LGA and iPTB. Weight gains associated with probabilities of SGA and LGA of < or =10% and a minimal risk of iPTB and sPTB were as follows: 9.1-13.5 kg (obesity class 1), 5.0-9 kg (obesity class 2), 2.2 to <5.0 kg (obesity class 3 white women), and <2.2 kg (obesity class 3 black women).
  
  
  CONCLUSIONS
  These data suggest that the range of gestational weight gain to balance risks of SGA, LGA, sPTB, and iPTB may vary by severity of obesity.
authors.affiliation: Department of Epidemiology, University of Pittsburgh, PA 15261, USA. bodnar@edc.pitt.edu <bodnar@edc.pitt.edu>
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Bodnar
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Siega-Riz
authors.forename: Hyagriv N
authors.initials: HN
authors.lastname: Simhan
authors.forename: Katherine P
authors.initials: KP
authors.lastname: Himes
authors.forename: Barbara
authors.initials: B
authors.lastname: Abrams
mesh_terms: D005260:Female; D005320:Fetal Macrosomia / Q000453:epidemiology / Q000503:physiopathology; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology; D007236:Infant, Small for Gestational Age / Q000502:physiology; D016015:Logistic Models; D015999:Multivariate Analysis; D009765:Obesity / Q000453:epidemiology* / Q000503:physiopathology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology* / Q000503:physiopathology; D011256:Pregnancy Outcome / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D015430:Weight Gain