title: Prediction of preterm birth in multiple pregnancies: development of a multivariable model including cervical length measurement at 16 to 21 weeks' gestation.
abstract: OBJECTIVE
  To develop a multivariable prognostic model for the risk of preterm delivery in women with multiple pregnancy that includes cervical length measurement at 16 to 21 weeks' gestation and other variables.
  
  
  METHODS
  We used data from a previous randomized trial. We assessed the association between maternal and pregnancy characteristics including cervical length measurement at 16 to 21 weeks' gestation and time to delivery using multivariable Cox regression modelling. Performance of the final model was assessed for the outcomes of preterm and very preterm delivery using calibration and discrimination measures.
  
  
  RESULTS
  We studied 507 women, of whom 270 (53%) delivered < 37 weeks (preterm) and 66 (13%) < 32 weeks (very preterm). Women with cervical length < 30 mm delivered more often preterm (hazard ratio 1.9; 95% CI 0.7 to 4.8). Other independently contributing predictors were previous preterm delivery, monochorionicity, smoking, educational level, and triplet pregnancy. Prediction models for preterm and very preterm delivery had a c-index of 0.68 (95% CI 0.63 to 0.72) and 0.68 (95% CI 0.62 to 0.75), respectively, and showed good calibration.
  
  
  CONCLUSIONS
  In women with a multiple pregnancy, the risk of preterm delivery can be assessed with a multivariable model incorporating cervical length and other predictors.
authors.affiliation: VU University Medical Center, the Netherlands.
authors.forename: Lidewij
authors.initials: L
authors.lastname: van de Mheen
authors.affiliation: Julius Center for Health Sciences and Primary Care, Utrecht, the Netherlands; Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Ewoud
authors.initials: E
authors.lastname: Schuit
authors.affiliation: Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Arianne C
authors.initials: AC
authors.lastname: Lim
authors.affiliation: Maxima Medical Center, Veldhoven, the Netherlands.
authors.forename: Martina M
authors.initials: MM
authors.lastname: Porath
authors.affiliation: Amphia Hospital, Breda, the Netherlands.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Papatsonis
authors.affiliation: University Medical Center, Groningen, the Netherlands.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Erwich
authors.affiliation: Isala Clinics, Zwolle, the Netherlands.
authors.forename: Jim
authors.initials: J
authors.lastname: van Eyck
authors.affiliation: St. Elizabeth Hospital, Tilburg, the Netherlands.
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: van Oirschot
authors.affiliation: Medical Center, Alkmaar, the Netherlands.
authors.forename: Piet
authors.initials: P
authors.lastname: Hummel
authors.affiliation: Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Duvekot
authors.affiliation: Catharina Hospital, Eindhoven, the Netherlands.
authors.forename: Tom H M
authors.initials: TH
authors.lastname: Hasaart
authors.affiliation: Julius Center for Health Sciences and Primary Care, Utrecht, the Netherlands.
authors.forename: Rolf H H
authors.initials: RH
authors.lastname: Groenwold
authors.affiliation: Julius Center for Health Sciences and Primary Care, Utrecht, the Netherlands.
authors.forename: Karl G M
authors.initials: KG
authors.lastname: Moons
authors.affiliation: VU University Medical Center, the Netherlands.
authors.forename: Christianne J M
authors.initials: CJ
authors.lastname: de Groot
authors.affiliation: University Medical Center, Utrecht, the Netherlands.
authors.forename: Hein W
authors.initials: HW
authors.lastname: Bruinse
authors.affiliation: Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands.
authors.forename: Maria G
authors.initials: MG
authors.lastname: van Pampus
authors.affiliation: The Robinson Institute, School of Reproductive and Paediatric Health, University of Adelaide, Australia.
authors.forename: Ben W J
authors.initials: BW
authors.lastname: Mol
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D004522:Educational Status; D005260:Female; D005865:Gestational Age; D006801:Humans; D015999:Multivariate Analysis; D011247:Pregnancy; D011272:Pregnancy, Multiple; D047928:Premature Birth; D012907:Smoking / Q000009:adverse effects
keywords: cervical length measurement; multiple pregnancy; prediction; preterm birth