title: Nulliparity and preterm birth in the era of obesity epidemic.
abstract: OBJECTIVE
  To assess the impact of obesity on preterm birth among nulliparous women.
  
  
  METHODS
  Retrospective cohort study of nulliparous mothers delivering infants in Florida between 2004 and 2007. Women were classified as non-obese (pre-pregnancy body mass index (BMI) <30) or obese (BMI ≥ 30). The main outcomes assessed were preterm birth, very preterm birth and extremely preterm birth. Risk estimates were obtained using logistic regression. Multiparous non-obese mothers were the referent group for all analyses.
  
  
  RESULTS
  As compared to multiparous women, nulliparous mothers had an increased risk of very preterm and extremely preterm birth with the highest risk observed for extremely preterm birth (odds ratios (OR) = 1.37, 95% CI = 1.28, 1.47) (p for trend <0.01). Obese nulliparous mothers had an elevated risk of preterm, very preterm and extremely preterm birth, with the risk of extremely preterm birth being the most pronounced (OR=1.97, 95% CI=1.75-2.22) [p for trend <0.05]. The heightened risk associated with obesity among nulliparous women was observed across all racial/ethnic sub-populations, with black nulliparous obese mothers being at greatest risk of all preterm birth-subtypes.
  
  
  CONCLUSIONS
  Obesity is a risk marker for preterm, very preterm and extremely preterm birth among first-time mothers and particularly among blacks and Hispanics.
authors.affiliation: The Chiles Center for Healthy Mothers and Babies, University of South Florida, Tampa, FL 33613, USA. hamisu.salihu@gmail.com
authors.forename: Hamisu
authors.initials: H
authors.lastname: Salihu
authors.forename: Alfred K
authors.initials: AK
authors.lastname: Mbah
authors.forename: Amina P
authors.initials: AP
authors.lastname: Alio
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kornosky
authors.forename: Valerie E
authors.initials: VE
authors.lastname: Whiteman
authors.forename: Victoria
authors.initials: V
authors.lastname: Belogolovkin
authors.forename: Lewis P
authors.initials: LP
authors.lastname: Rubin
mesh_terms: D000328:Adult; D001724:Birth Weight; D044383:Black People; D015992:Body Mass Index; D015331:Cohort Studies; D005006:Ethnicity; D005260:Female; D005865:Gestational Age; D006630:Hispanic or Latino; D006801:Humans; D016015:Logistic Models; D009765:Obesity / Q000150:complications*; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D047928:Premature Birth / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors