title: Cervical length at 18-22 weeks of gestation for prediction of spontaneous preterm delivery in Hong Kong Chinese women.
abstract: OBJECTIVE
  To assess the value of a single cervical length measurement by transvaginal sonography (TVS) at the time of mid-trimester anomaly scan for predicting spontaneous preterm delivery (SPD) among Chinese women.
  
  
  METHODS
  A prospective observational study was carried out involving 2880 subjects with singleton pregnancies and confirmed gestational age. Cervical length was measured at 18-22 weeks of gestation.
  
  
  RESULTS
  The incidence of SPD < 34 weeks and < 37 weeks were 0.7% and 3.7%, respectively. Women with SPD < 34 weeks and SPD < 37 weeks had shorter median cervical lengths (32.6 mm and 36.2 mm, respectively) than those with term deliveries (37.6 mm) (P = 0.006 and 0.025, respectively). The predictive performance of cervical length was better for SPD < 34 weeks compared with < 37 weeks. A cervical length < or = 27 mm, which corresponded to the 4th centile, occurred in 36.8%, 62.5% and 100% of those with SPD < 34, < 30 and < 26 weeks, respectively. The positive likelihood ratio (LR) of a cervical length < or = 27 mm in predicting SPD < 34 weeks was 9.8. Using logistic regression, both short cervix and funneling were independent predictors for SPD < 34 weeks of gestation. The coexistence of funneling and a cervical length < or = 27 mm gave a positive predictive value (PPV) and LR of SPD < 34 weeks of 14.7% and 26.0, respectively.
  
  
  CONCLUSIONS
  Mid-trimester cervical length is predictive of SPD in Chinese women. However, given the low PPV of a short cervical length, its clinical utility is still limited in low-risk populations.
authors.affiliation: Fetal Medicine Unit, Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, The Prince of Wales Hospital, Hong Kong. leungtn@yahoo.com.hk
authors.forename: T N
authors.initials: TN
authors.lastname: Leung
authors.forename: M W
authors.initials: MW
authors.lastname: Pang
authors.forename: T Y
authors.initials: TY
authors.lastname: Leung
authors.forename: C F
authors.initials: CF
authors.lastname: Poon
authors.forename: S M
authors.initials: SM
authors.lastname: Wong
authors.forename: T K
authors.initials: TK
authors.lastname: Lau
mesh_terms: D000328:Adult; D044466:Asian People; D020070:Cervical Ripening / Q000208:ethnology; D002584:Cervix Uteri / Q000000981:diagnostic imaging* / Q000473:pathology; D004812:Epidemiologic Methods; D005260:Female; D005865:Gestational Age; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging* / Q000208:ethnology / Q000473:pathology; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000208:ethnology; D014463:Ultrasonography