title: Prediction of delivery among women with early preterm labor by means of clinical characteristics alone.
abstract: OBJECTIVE
  This study was undertaken to assess whether individual clinical factors or combinations thereof could be used to accurately predict the risk of delivery within 1 week of admission among women with preterm labor and minimal cervical dilatation.
  
  
  METHODS
  We performed a case-control study of patients admitted to our institution with preterm labor and minimal cervical dilatation. A case patient was a patient who sought treatment with uterine contractions between 24 and 34 weeks' gestation with cervical dilatation </=2 cm, who received tocolysis with magnesium sulfate, and who was delivered within 7 days of admission. Control subjects were those who had the same presentation with preterm labor but were not delivered within the first 7 days after admission. The medical records of case patients and control subjects were then abstracted, and information on >70 potential predictors was recorded. Statistical analysis consisted of bivariate and multivariable methods. We also generated a multivariable clinical predictive model with the purpose of detecting a proportion as high as possible of those destined to be delivered within 1 week (high sensitivity). We estimated that we would need 50 case patients and 150 control subjects to detect an odds ratio of 2.5 for risk factors with a prevalence of 20%, an alpha error of.05, a beta error of.20, and a control subject/case patient ratio of 3:1.
  
  
  RESULTS
  Three variables were eligible for inclusion in our logistic models according to the bivariate analyses-bleeding on admission, substance abuse, and admission white blood cell count >/=14,000 cells/microL. The simplest and most favorable model included only 2 variables, bleeding and substance abuse, and yielded a sensitivity of 46% and a specificity of 76%. The full 3-variable model had similar test characteristics. For no model were we able to achieve a sensitivity >/=50%.
  
  
  CONCLUSIONS
  The results of this case-control study suggest that combinations of clinical factors do not yield an adequate level of discrimination to be used alone for predicting the likelihood of delivery within 1 week among patients with minimal degrees of cervical dilatation.
authors.affiliation: Department of Obstetrics and Gynecology, University of Pennsylvania Health System, Philadelphia, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Macones
authors.forename: S Y
authors.initials: SY
authors.lastname: Segel
authors.forename: D M
authors.initials: DM
authors.lastname: Stamilio
authors.forename: M A
authors.initials: MA
authors.lastname: Morgan
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007958:Leukocyte Count; D016015:Logistic Models; D008278:Magnesium Sulfate / Q000627:therapeutic use; D015999:Multivariate Analysis; D007752:Obstetric Labor, Premature / Q000517:prevention & control; D016017:Odds Ratio; D010808:Physical Examination / Q000592:standards*; D011237:Predictive Value of Tests; D011247:Pregnancy; D012307:Risk Factors; D012680:Sensitivity and Specificity; D019966:Substance-Related Disorders / Q000150:complications; D015149:Tocolytic Agents / Q000627:therapeutic use; D014592:Uterine Hemorrhage / Q000150:complications
chemical_list: D015149:Tocolytic Agents; D008278:Magnesium Sulfate