title: The role of cervical length in women with threatened preterm labor: is it a valid predictor at any gestational age?
abstract: OBJECTIVE
  To determine whether the predictive accuracy of sonographic cervical length (CL) for preterm delivery (PTD) in women with threatened preterm labor (PTL) is related to gestational age (GA) at presentation.
  
  
  METHODS
  A retrospective cohort study of all women with singleton pregnancies who presented with PTL at less than 34 + 0 weeks and underwent sonographic measurement of CL in a tertiary medical center between 2007 and 2012. The predictive accuracy of CL for PTD was stratified by GA at presentation.
  
  
  RESULTS
  Overall, 1077 women who presented with PTL have had sonographic measurement of CL and met the study inclusion criteria. Of those, 223 (20.7%) presented at 24 + 0-26 + 6 weeks (group 1), 274 (25.4%) at 27 + 0-29 + 6 weeks (group 2), 283 (26.3%) at 30 + 0-31 + 6 weeks (group 3), and 297 (27.6%) at 32 + 0-33 + 6 weeks (group 4). The overall performance CL as a predictive test for PTD was similar in the 4 GA groups, as reflected by the similar degree of correlation between CL with the examination to delivery interval (r = 0.27, r = 0.26, r = 0.28, and r = 0.29, respectively, P = .8), the similar area under the receiver-operator characteristic curve (0.641-0.690, 0.631-0.698, 0.643-0.654, and 0.678-0.698, respectively, P = .7), and a similar decrease in the risk of PTD of 5-10% for each additional millimeter of CL. The optimal cutoff of CL, however, was affected by GA at presentation, so that a higher cutoff of CL was needed to achieve a target negative predictive value for delivery within 14 days from presentation for women who presented later in pregnancy. The optimal thresholds to maximize the negative predictive value for delivery within 14 days were 36 mm, 32.5 mm, 24 mm and 20.5 mm for women who presented at 32 + 0 to 33 + 6 weeks, 30 + 0 to 31 + 6 weeks, 27 + 0 to 29 + 6 weeks and 24 + 0 to 26 + 6, respectively.
  
  
  CONCLUSIONS
  CL has modest predictive accuracy in women with threatened PTL, regardless of GA at presentation. However, the optimal cutoff of CL for the purpose of clinical decision making in women with PTL needs to be adjusted based on GA at presentation.
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Liran
authors.initials: L
authors.lastname: Hiersch
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Yariv
authors.initials: Y
authors.lastname: Yogev
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Noam
authors.initials: N
authors.lastname: Domniz
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Israel
authors.initials: I
authors.lastname: Meizner
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Bardin
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Melamed
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement / Q000706:statistics & numerical data*; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D047928:Premature Birth / Q000000981:diagnostic imaging*; D012372:ROC Curve; D012189:Retrospective Studies; D018570:Risk Assessment
keywords: cervical length; gestational age; preterm delivery