title: Association between sonographic cervical appearance and preterm delivery after a history-indicated cerclage.
abstract: OBJECTIVE
  To determine which transvaginal cervical sonographic characteristics are associated with preterm delivery after placement of a history-indicated cerclage.
  
  
  METHODS
  We conducted a case-control study of all women with a singleton gestation and a history-indicated cerclage placed at a single center between January 1, 2008, and October 1, 2012. Cerclages were placed between 12 and 16 weeks' gestation. Cases were defined as women who delivered before 34 weeks' gestation; controls delivered at or after 34 weeks. Transvaginal cervical characteristics, such as cervical funneling, proximal cervical length, distal cervical length, and total cervical length, obtained between 18 and 24 weeks were compared between the two groups. Bivariable, multivariable, and log rank analyses were performed.
  
  
  RESULTS
  A total of 124 women met inclusion criteria, with 17 (14%) delivering before 34 weeks. Cervical funneling, a proximal cervical length of less than 1.5 cm, and a total cervical length of less than 2.5 cm were associated with an increased odds of preterm birth before 34 weeks in the bivariable analysis [odds ratio (OR), 10.9 (95% confidence interval (CI), 2.3-62.8), 2.9 (95% CI, 1.0-8.5), and 4.5 (95% CI, 1.3-16.4), respectively], whereas distal cervical length of less than 1 cm was not significantly associated with delivery before 34 weeks [OR, 3.0 (95% CI, 0.8-11.1)]. In multivariable analysis, only cervical funneling remained associated with preterm delivery before 34 weeks [adjusted OR, 10.6 (95% CI, 2.2-51.5)].
  
  
  CONCLUSIONS
  In women with a history-indicated cerclage, cervical funneling is the only independently significant sonographic finding associated with an increased risk of preterm birth before 34 weeks.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA. emily-miller-1@fsm.northwestern.edu.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Miller
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Gerber
mesh_terms: D016022:Case-Control Studies; D015984:Causality; D023802:Cerclage, Cervical / Q000706:statistics & numerical data*; D054791:Cervical Length Measurement / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007087:Illinois / Q000453:epidemiology; D008487:Medical History Taking / Q000706:statistics & numerical data*; D011247:Pregnancy; D047928:Premature Birth / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D015995:Prevalence; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D002581:Uterine Cervical Incompetence / Q000000981:diagnostic imaging* / Q000453:epidemiology*
keywords: cerclage; cervical funneling; cervical insufficiency; cervical length; obstetric ultrasound; preterm birth