title: The association of inadequate mid-pregnancy weight gain and preterm birth in twin pregnancies.
abstract: OBJECTIVE
  To determine whether inadequate gestational weight gain in the second trimester in twin pregnancies is associated with an increased risk of preterm birth (PTB) at <32 weeks.
  
  
  METHODS
  Retrospective cohort study including 489 twin pregnancies delivered between 2001 and 2013. Rates of weight gain at different gestational ages were compared with Institute of Medicine guidelines.
  
  
  RESULTS
  An inadequate rate of weight gain at <20 weeks was not associated with PTB. Patients with inadequate rates of weight gain at 20 to 28 weeks had a higher risk of PTB at <32 weeks (37.6%) compared to those with adequate weight gain (15.2%) (P<0.001). In multivariate analysis, women with inadequate weight gain at 20 to 28 weeks were 2.8 times more likely to deliver at <32 weeks (95% confidence interval 1.65 to 4.81).
  
  
  CONCLUSIONS
  Inadequate gestational weight gain at 20 to 28 weeks in twin pregnancies was the strongest predictor of PTB at <32 weeks. This represents an optimal time for interventions to improve weight gain and potentially decrease rates of PTB.
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Pettit
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: D Y
authors.initials: DY
authors.lastname: Lacoursiere
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Schrimmer
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: H
authors.initials: H
authors.lastname: Alblewi
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Moore
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Ramos
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D011262:Pregnancy Trimester, Second; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D012189:Retrospective Studies; D012307:Risk Factors; D013223:Statistics as Topic; D014481:United States; D015430:Weight Gain / Q000502:physiology*