title: Correlation Between Cervical Lengths Measured by Transabdominal and Transvaginal Sonography for Predicting Preterm Birth.
abstract: OBJECTIVE
  Cervical length assessment is important for predicting preterm birth. Cervical length measurement using transabdominal sonography is more comfortable for the patient but has more limitations than transvaginal sonography. Our aim was to determine whether transabdominal sonography could identify those women who should undergo transvaginal sonography for prediction of preterm birth.
  
  
  METHODS
  In this prospective study, women underwent cervical length measurements by transabdominal and transvaginal sonography between 20 and 29 gestational weeks and were followed until delivery. We assessed whether short cervical lengths on transabdominal sonography could predict short cervical lengths on transvaginal sonography and whether these measurements could predict preterm births (<34 gestational weeks).
  
  
  RESULTS
  The mean cervical lengths were not significantly different between the techniques (mean ± SD, 3.78 ± 0.82 and 3.82 ± 0.77 cm on transabdominal and transvaginal sonography, respectively; P = .09). The sensitivity of short cervical lengths (<2 cm) on transabdominal sonography for prediction of short cervical lengths on transvaginal sonography was 100%. The sensitivity, specificity, positive predictive value, negative predictive value, and relative risk of short cervical lengths (<2 cm) for predicting preterm birth were 21.4%, 98.68%, 50.00%, 95.32%, and 13.22 when using transabdominal sonography and 28.57%, 94.94%, 66.6%, 95.74%, and 17.78 when using transvaginal sonography, respectively. In an analysis that included cases with transabdominal sonography, the sensitivity of short cervical lengths for predicting preterm birth was increased.
  
  
  CONCLUSIONS
  Women whose cervical lengths are measurable and long on transabdominal sonography may not need transvaginal sonography. Women whose cervical lengths are unmeasurable or short (<2 or <2.5 cm) on transabdominal sonography should undergo transvaginal sonography to measure cervical lengths for prediction of preterm birth.
authors.affiliation: Department of Obstetrics and Gynecology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea (H.J.C.); and Department of Obstetrics and Gynecology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea (H.-J.R.).
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Cho
authors.affiliation: Department of Obstetrics and Gynecology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea (H.J.C.); and Department of Obstetrics and Gynecology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea (H.-J.R.). dr-nhj@hanmail.net.
authors.forename: Hyun-Jin
authors.initials: HJ
authors.lastname: Roh
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging; D000328:Adult; D054791:Cervical Length Measurement / Q000379:methods*; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D047928:Premature Birth / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014621:Vagina / Q000000981:diagnostic imaging; D055815:Young Adult
keywords: cervical length; obstetric ultrasound; prediction of preterm birth; transabdominal sonography; transvaginal sonography