title: Gestational weight gain in obese mothers and associations with fetal growth.
abstract: BACKGROUND
  In 2009, the Institute of Medicine recommended gestational weight gains (GWGs) of 5-9 kg for all obese women. Recommendations by severity of obesity were not specified because of a lack of available data.
  
  
  OBJECTIVE
  Our objective was to examine associations between GWG and fetal growth in obese women and assess interactions with obesity severity.
  
  
  METHODS
  We used 2004-2006 Pregnancy Nutrition Surveillance System data from 122,327 obese mothers [prepregnant body mass index (BMI; in kg/m(2)) ge 30]. We used logistic regression to estimate measures of fetal growth including small-for-gestational-age, which was defined as birth weight (BW) lt 2 SDs below the sex and race-ethnicity-specific mean BW (SGA(2SD)), and macrosomia (BW ge 4500 g). We tested for interactions between obesity severity (class I: BMI of 30-34.9; class II: BMI of 35.0-39.9; class III: BMI ge 40) and GWG.
  
  
  RESULTS
  Obesity severity modified associations between GWG and fetal growth. Compared with weight gains of 5-9 kg, weight loss in class I women significantly increased the odds of SGA(2SD), whereas a GWG from 0.1 to 4.9 kg was not associated with SGA(2SD) and did not decrease the odds of macrosomia. In class II and III women, compared with weight gains of 5-9 kg, a GWG from minus 4.9 to +4.9 kg was not associated with SGA(2SD) but did decrease the odds of macrosomia.
  
  
  CONCLUSIONS
  Our study suggests a GWG below the Institute of Medicine guidelines may be associated with more favorable BW for all obese women, and GWG may need to be further defined by obesity severity.
authors.affiliation: Emory University, Atlanta, GA, USA.
authors.forename: Stefanie N
authors.initials: SN
authors.lastname: Hinkle
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Sharma
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Dietz
mesh_terms: D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D005260:Female; D047109:Fetal Development; D005320:Fetal Macrosomia / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D016015:Logistic Models; D008297:Male; D009765:Obesity / Q000145:classification / Q000150:complications*; D011247:Pregnancy / Q000502:physiology*; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index; D015430:Weight Gain; D015431:Weight Loss; D055815:Young Adult