title: Predicting risk of spontaneous preterm delivery in women with a singleton pregnancy.
abstract: BACKGROUND
  Prediction of a woman's risk of a spontaneous preterm delivery (PTD) is a core challenge and an unresolved problem in today's obstetric practice. The objective of this study was to develop prediction models for spontaneous PTD (<37 weeks).
  
  
  METHODS
  A population-based register study of women born in Sweden with spontaneous onset of delivery was designed using Swedish Medical Birth Register data for 1992-2008. Predictive variables were identified by multiple logistic regression analysis, and outputs were used to calculate adjusted likelihood ratios in primiparous (n = 199 272) and multiparous (n = 249 580) singleton pregnant women. The predictive ability of each model was validated in a separate test sample for primiparous (n = 190 936) and multiparous (n = 239 203) women, respectively.
  
  
  RESULTS
  For multiparous women, the area under the ROC curve (AUC) of 0.74 [95% confidence interval (CI) 0.73, 0.74] indicated a satisfying performance of the model, while for primiparous women, it was rather poor {AUC: 0.58 [95% CI 0.57, 0.58]}. For both primiparous and multiparous women, the prediction models were quite good for pregnancies with comparatively low risk for spontaneous PTD, whereas more limited to predict pregnancies with ≥30% risk of spontaneous PTD.
  
  
  CONCLUSIONS
  Spontaneous PTD is difficult to predict in multiparous women and nearly impossible in primiparous, by using this statistical method in a large and unselected sample. However, adding clinical data (like cervical length) may in the future further improve its predictive performance.
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway; National Institute of Environmental Health Sciences, Epidemiology Branch, Durham, NC; Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Nils-Halvdan
authors.initials: NH
authors.lastname: Morken
authors.forename: Karin
authors.initials: K
authors.lastname: Källen
authors.forename: Bo
authors.initials: B
authors.lastname: Jacobsson
mesh_terms: D000328:Adult; D019540:Area Under Curve; D054791:Cervical Length Measurement / Q000379:methods*; D002584:Cervix Uteri / Q000473:pathology*; D036861:Delivery, Obstetric; D005260:Female; D005322:Premature Rupture of Fetal Membranes; D006801:Humans; D007231:Infant, Newborn; D007752:Obstetric Labor, Premature / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000175:diagnosis* / Q000453:epidemiology; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013548:Sweden
keywords: predicting risk; singleton pregnancy; spontaneous preterm delivery