title: Cervical length changes from the first to second trimester of pregnancy, and prediction of preterm birth by first-trimester sonographic cervical measurement.
abstract: OBJECTIVE
  The purpose of this study was to examine the evolution of cervical length from the first to second trimester of pregnancy and the value of first-trimester cervical measurement in the prediction of preterm delivery.
  
  
  METHODS
  We conducted a longitudinal prospective study. Cervical length was measured by transvaginal sonography at 11 to 14 weeks (Cx1), 16 to 19 weeks (Cx2), and 20 to 24 weeks (Cx3).
  
  
  RESULTS
  Eight hundred singleton pregnancies were studied. The median cervical lengths were 33 mm for Cx1 and 31 mm for Cx2 and Cx3. Significant independent predictors for cervical length were maternal weight, height, and history of cervical surgery for Cx1, maternal height, history of cervical surgery, and history of preterm delivery for Cx2, and history of cervical surgery, history of first-trimester miscarriage, and history of spontaneous preterm delivery for Cx3. Mean cervical length shortening was 2.36 mm between Cx1 and Cx3. In the subgroups of women with previous cervical surgery and history of previous preterm birth, cervical shortening was significantly more prominent. The median Cx1 was significantly shorter in the women who subsequently delivered preterm; Cx1 predicted preterm delivery before 34 weeks (odds ratio, 0.746; 95% confidence interval, 0.649-0.869) and preterm delivery before 32 weeks (odds ratio, 0.734; 95% confidence interval, 0.637-0.912).
  
  
  CONCLUSIONS
  Cervical length in the first trimester depends on maternal characteristics and a history of cervical surgery. The cervix exhibits minimal changes from 11 to 24 weeks for most women, although the shortening is more prominent in women with a history of cervical surgery or preterm delivery. First-trimester cervical length measurement can predict preterm delivery.
authors.affiliation: Third Department of Obstetrics and Gynecology, Attikon University Hospital, Rimini 1, Haidari, 124-62 Athens, Greece. athena.souka@googlemail.com
authors.forename: Athena P
authors.initials: AP
authors.lastname: Souka
authors.forename: Ioannis
authors.initials: I
authors.lastname: Papastefanou
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Michalitsi
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Salambasis
authors.forename: Charalambos
authors.initials: C
authors.lastname: Chrelias
authors.forename: George
authors.initials: G
authors.lastname: Salamalekis
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kassanos
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002584:Cervix Uteri / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D047928:Premature Birth / Q000473:pathology*; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods*