title: Spontaneous and indicated preterm delivery risk is increased among overweight and obese women without prepregnancy chronic disease.
abstract: OBJECTIVE
  To investigate the independent impact of prepregnancy obesity on preterm delivery among women without chronic diseases by gestational age, preterm category and parity.
  
  
  METHODS
  A retrospective cohort study.
  
  
  METHODS
  Data from the Consortium on Safe Labor (CSL) in the USA (2002-08).
  
  
  METHODS
  Singleton deliveries at ≥23 weeks of gestation in the CSL (43 200 nulliparas and 63 129 multiparas) with a prepregnancy body mass index (BMI) ≥18.5 kg/m2and without chronic diseases.
  
  
  METHODS
  Association of prepregnancy BMI and the risk of preterm delivery was examined using Poisson regression with normal weight as reference.
  
  
  METHODS
  Preterm deliveries were categorised by gestational age (extremely, very, moderate to late) and category (spontaneous, indicated, no recorded indication).
  
  
  RESULTS
  Relative risk of spontaneous preterm delivery was increased for extremely preterm among obese nulliparas (1.26, 95% CI: 0.94-1.70 for overweight; 1.88, 95% CI: 1.30-2.71 for obese class I; 1.99, 95% CI: 1.32-3.01 for obese class II/III) and decreased for moderate to late preterm delivery among overweight and obese multiparas (0.90, 95% CI: 0.83-0.97 for overweight; 0.87, 95% CI: 0.78-0.97 for obese class I; 0.79, 95% CI: 0.69-0.90 for obese class II/III). Indicated preterm delivery risk was increased with prepregnancy BMI in a dose-response manner for extremely preterm and moderate to late preterm among nulliparas, as it was for moderate to late preterm delivery among multiparas.
  
  
  CONCLUSIONS
  Prepregnancy BMI was associated with increased risk of preterm delivery even in the absence of chronic diseases, but the association was heterogeneous by preterm categories, gestational age and parity.
  
  
  CONCLUSIONS
  Obese nulliparas without chronic disease had higher risk for spontaneous delivery <28 weeks of gestation.
authors.affiliation: Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.|Division of Epidemiology and Health Index, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: S S
authors.initials: SS
authors.lastname: Kim
authors.affiliation: Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
authors.forename: P
authors.initials: P
authors.lastname: Mendola
authors.affiliation: Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.|Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Biostatistics and Bioinformatics Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.|Department of Applied Statistics, Chung-Ang University, Seoul, Korea.
authors.forename: B S
authors.initials: BS
authors.lastname: Hwang
authors.affiliation: Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Grantz
mesh_terms: D000328:Adult; D015992:Body Mass Index; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D009765:Obesity / Q000150:complications / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome; D037841:Pregnant People; D047928:Premature Birth / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
keywords: Medically indicated delivery; obesity; pregnancy; prepregnancy obesity; preterm delivery; spontaneous delivery