title: A stillbirth calculator: Development and internal validation of a clinical prediction model to quantify stillbirth risk.
abstract: OBJECTIVE
  To generate a clinical prediction tool for stillbirth that combines maternal risk factors to provide an evidence based approach for the identification of women who will benefit most from antenatal testing for stillbirth prevention.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Midwestern United States quaternary referral center.
  
  
  METHODS
  Singleton pregnancies undergoing second trimester anatomic survey from 1999-2009. Pregnancies with incomplete follow-up were excluded.
  
  
  METHODS
  Candidate predictors were identified from the literature and univariate analysis. Backward stepwise logistic regression with statistical comparison of model discrimination, calibration and clinical performance was used to generate final models for the prediction of stillbirth. Internal validation was performed using bootstrapping with 1,000 repetitions. A stillbirth risk calculator and stillbirth risk score were developed for the prediction of stillbirth at or beyond 32 weeks excluding fetal anomalies and aneuploidy. Statistical and clinical cut-points were identified and the tools compared using the Integrated Discrimination Improvement.
  
  
  METHODS
  Antepartum stillbirth.
  
  
  RESULTS
  64,173 women met inclusion criteria. The final stillbirth risk calculator and score included maternal age, black race, nulliparity, body mass index, smoking, chronic hypertension and pre-gestational diabetes. The stillbirth calculator and simple risk score demonstrated modest discrimination but clinically significant performance with no difference in overall performance between the tools [(AUC 0.66 95% CI 0.60-0.72) and (AUC 0.64 95% CI 0.58-0.70), (p = 0.25)].
  
  
  CONCLUSIONS
  A stillbirth risk score was developed incorporating maternal risk factors easily ascertained during prenatal care to determine an individual woman's risk for stillbirth and provide an evidenced based approach to the initiation of antenatal testing for the prediction and prevention of stillbirth.
authors.affiliation: Mercy Hospital St. Louis Department of Obstetrics and Gynecology, Midwest Maternal Fetal Medicine, St. Louis, Missouri, United States of America.
authors.forename: Amanda S
authors.identifier: http://orcid.org/0000-0002-2934-6019
authors.initials: AS
authors.lastname: Trudell
authors.affiliation: Washington University School of Medicine Department of Obstetrics and Gynecology Division of Maternal Fetal Medicine, St. Louis, Missouri, United States of America.
authors.forename: Methodius G
authors.initials: MG
authors.lastname: Tuuli
authors.affiliation: Washington University School of Medicine Department of Surgery Division of Public Health, St. Louis, Missouri, United States of America.
authors.forename: Graham A
authors.initials: GA
authors.lastname: Colditz
authors.affiliation: Washington University School of Medicine Department of Obstetrics and Gynecology Division of Maternal Fetal Medicine, St. Louis, Missouri, United States of America.
authors.forename: George A
authors.initials: GA
authors.lastname: Macones
authors.affiliation: University of South Florida, Moorsani College of Medicine Department of Obstetrics and Gynecology Division of Maternal Fetal Medicine, Tampa, Florida, United States of America.
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
mesh_terms: D000328:Adult; D000782:Aneuploidy; D015897:Comorbidity; D016208:Databases, Factual; D005260:Female; D006801:Humans; D015233:Models, Statistical; D016017:Odds Ratio; D011247:Pregnancy; D011379:Prognosis; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D050497:Stillbirth