title: Prospective validation of two models predicting pregnancy leading to live birth among untreated subfertile couples.
abstract: BACKGROUND
  Models predicting clinical outcome need external validation before they can be applied safely in daily practice. This study aimed to validate two models for the prediction of the chance of treatment-independent pregnancy leading to live birth among subfertile couples.
  
  
  METHODS
  The first model uses the woman's age, duration and type of subfertility, percentage of progressive sperm motility and referral status. The second model in addition uses the result of the post-coital test (PCT). For validation, these characteristics were collected prospectively in two University hospitals for 302 couples consulting for subfertility. The models' ability to distinguish between women who became pregnant and women who did not (discrimination) and the agreement between predicted and observed probabilities of treatment-independent pregnancy (calibration) were assessed.
  
  
  RESULTS
  The discrimination of both models was slightly lower in the validation sample than in the original sample which provided the model. Calibration was good: the observed and predicted probabilities of treatment-independent pregnancy leading to live birth did not differ for both models.
  
  
  CONCLUSIONS
  The chance of pregnancy leading to live birth was reliably estimated in the validation sample by both models. The use of PCT improved the discrimination of the models. These models can be useful in counselling subfertile couples.
authors.affiliation: Department of Public Health, Division of Reproductive Medicine, Erasmus MC University Medical Center Rotterdam, PO Box 1738, 3000 DR Rotterdam, The Netherlands. c.hunault@erasmusmc.nl
authors.forename: Claudine C
authors.initials: CC
authors.lastname: Hunault
authors.forename: Joop S E
authors.initials: JS
authors.lastname: Laven
authors.forename: Ilse A J
authors.initials: IA
authors.lastname: van Rooij
authors.forename: Marinus J C
authors.initials: MJ
authors.lastname: Eijkemans
authors.forename: Egbert R
authors.initials: ER
authors.lastname: te Velde
authors.forename: J Dik F
authors.initials: JD
authors.lastname: Habbema
mesh_terms: D001723:Birth Rate; D003075:Coitus; D003944:Diagnostic Techniques, Obstetrical and Gynecological; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007246:Infertility / Q000209:etiology*; D008297:Male; D008423:Maternal Age; D008962:Models, Theoretical; D036801:Parturition; D011247:Pregnancy; D015203:Reproducibility of Results; D013081:Sperm Motility