title: The change in cervical length over time as a predictor of preterm delivery in asymptomatic women with twin pregnancies who have a normal mid-trimester cervical length.
abstract: OBJECTIVE
  To determine whether or not the change in cervical length (CL) over time is valuable in predicting spontaneous preterm delivery (SPTD) in asymptomatic twin pregnancies with a normal mid-trimester CL (>25 mm).
  
  
  METHODS
  This was a prospective study including 190 consecutive asymptomatic twin gestations with a CL>25 mm at 20-24 weeks. The women underwent an initial CL measurement at the time of routine ultrasound examination between 20 and 24 weeks' gestation, followed 4-5 weeks later by a repeat CL measurement. The primary outcome measure was SPTD at <32 completed weeks' gestation. Multicollinearity was a concern in the multivariable model since change in CL and follow-up CL were highly correlated.
  
  
  RESULTS
  The rate of SPTD at <32 weeks was 4.2%. Multiple logistic regression analyses demonstrated that the change in CL and the follow-up CL were significantly associated with SPTD before 32 weeks after adjusting for baseline covariate such as in vitro fertilization. The best cut-off values for the prediction of SPTD at <32 weeks' gestation were 13% for the change in CL with a sensitivity of 87.5% and a specificity of 63.2%. There was no significant difference in the area under the receiver operating characteristic curves between the change in CL and the follow-up CL.
  
  
  CONCLUSIONS
  A greater change in CL is a good predictor of SPTD in asymptomatic twin pregnancies with a normal mid-trimester CL. However, the change in CL cannot provide data beyond the follow-up CL. In the setting of a normal mid-trimester CL, a follow-up CL measurement should be considered in asymptomatic twin pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam-si, Korea.
authors.forename: Kyung Joon
authors.initials: KJ
authors.lastname: Oh
authors.forename: Kyo Hoon
authors.initials: KH
authors.lastname: Park
authors.forename: Eun Ha
authors.initials: EH
authors.lastname: Jeong
authors.forename: Sung Youn
authors.initials: SY
authors.lastname: Lee
authors.forename: Aeli
authors.initials: A
authors.lastname: Ryu
authors.forename: Shi-Nae
authors.initials: SN
authors.lastname: Kim
mesh_terms: D000328:Adult; D002584:Cervix Uteri / Q000000981:diagnostic imaging* / Q000473:pathology; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D016015:Logistic Models; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D059285:Pregnancy, Twin; D047928:Premature Birth / Q000000981:diagnostic imaging; D011446:Prospective Studies; D012372:ROC Curve; D056910:Republic of Korea; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D016216:Ultrasonography, Prenatal