title: Predictive Value of Initial Cervical Length for Subsequent Cervical Length Shortening in Women with a Prior Preterm Birth.
abstract: OBJECTIVE
  The objective of this study was to estimate the predictive value of the initial cervical length (CL) for later CL shortening in women at high risk for recurrent spontaneous preterm birth (SPTB). Materials and
  
  
  METHODS
  We conducted a secondary analysis of a multicenter randomized trial of high-risk women with CL screening scheduled at least every 2 weeks from 16(0/7) to 22(6/7) weeks. Primary outcome was CL < 25 mm or SPTB before follow-up CL; the risk of this outcome was analyzed by initial CL at 16(0/7) to 21(6/7) weeks using multivariable logistic regression and receiver operator curves.
  
  
  RESULTS
  A total of 786 women were identified in the parent trial; 197 (25.0%) developed CL shortening < 23 weeks, 3 (0.4%) delivered within 2 weeks of initial CL measurement (< 24 weeks), and 586 (74.6%) maintained CL ≥ 25 mm. The covariate-adjusted receiver operator characteristics curve had moderate predictive value (area under the curve = 0.748) but did not reveal a clinically useful CL cutoff. Evaluation of selected CL cutoffs demonstrated that an initial CL ≥39 mm had the greatest negative predictive value (85.1%). No CL cutoff existed above which there was no CL shortening, although at ≥ 39 mm only two patients (1.1%) shortened within 2 weeks as compared with 32 (7.1%) patients whose initial CL was < 39 mm (p < 0.001).
  
  
  CONCLUSIONS
  In high-risk patients whose initial CL is ≥ 39 mm, CL shortening or delivery is uncommon in the following 2 weeks. Patients with initial CL above this threshold may require less frequent surveillance.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama.
authors.forename: Akila
authors.initials: A
authors.lastname: Subramaniam
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama.
authors.forename: Lorie M
authors.initials: LM
authors.lastname: Harper
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama.
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Szychowski
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama.
authors.forename: John
authors.initials: J
authors.lastname: Owen
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D047928:Premature Birth / Q000175:diagnosis*; D012372:ROC Curve; D012307:Risk Factors; D055815:Young Adult