title: Can transabdominal ultrasound be used as a screening test for short cervical length?
abstract: OBJECTIVE
  Universal transvaginal cervical length screening can be associated with a significant logistical burden. We hypothesized that there is a threshold cervical length measured by transabdominal ultrasound above which risk for short transvaginal cervical length is extremely low.
  
  
  METHODS
  This prospective cohort study evaluated a consecutive series of women offered universal transvaginal cervical length screening during anatomy ultrasound. Transabdominal measurement of the cervix-obtained before and after voiding for each patient-was performed before transvaginal ultrasound. The study was powered to detect a transabdominal cervical length cutoff with 95% sensitivity (95% confidence interval, 90-99%) for transvaginal cervical length of ≤25 mm.
  
  
  RESULTS
  One thousand two hundred seventeen women were included in the analysis. Prevoid transabdominal cervical length ≤36 mm detects 96% of transvaginal cervical lengths ≤25 mm with 39% specificity. A prevoid transabdominal cervical length ≤35 mm detects 100% of transvaginal cervical lengths ≤20 mm with 41% specificity. Transabdominal images of the cervix could not be obtained in 6.2% of women prevoid and 17.9% of women postvoid.
  
  
  CONCLUSIONS
  Transabdominal cervical length screening successfully identifies women at very low risk for short transvaginal cervical length. Transabdominal screening may significantly reduce the burden of universal cervical length screening by allowing approximately 40% of women to avoid transvaginal ultrasound. To ensure high sensitivity of transabdominal screening, approximately 60% of patients will still require a transvaginal study.
authors.affiliation: Maternal and Child Health Research Program, Department of Obstetrics and Gynecology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Friedman
authors.forename: Sindhu K
authors.initials: SK
authors.lastname: Srinivas
authors.forename: Samuel
authors.initials: S
authors.lastname: Parry
authors.forename: Michal A
authors.initials: MA
authors.lastname: Elovitz
authors.forename: Eileen
authors.initials: E
authors.lastname: Wang
authors.forename: Nadav
authors.initials: N
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*