title: [Transvaginal ultrasound assessment of cervical changes before onset of labor].
abstract: OBJECTIVE
  To study the clinical value of cervical measurement by transvaginal ultrasound after 36 weeks of gestation.
  
  
  METHODS
  Eighty three normal nulliparous woman were studied from 36 weeks of gestation until delivery prospectivelly. Transvaginal ultrasound examinations were performed and cervical length (CL), cervical width (CW) and the diameter of cervical canal were measured weekly. 52 cases were delivered naturelly and 31 cases by cesarean sections (CS).
  
  
  RESULTS
  From 36 weeks of gestation until delivery, there was a significant correlation between gestation age (GA) and CL and the diameter of cervical canal (r = -0.37, P < 0.00001; r = 0.16, P = 0.002). The time from examination to initiation of labor was significantly correlated with CL and the diameter of cervical canal (r = 0.32, P < 0.00001; r = -0.19, P = 0.02). The regressive formulas were CL (cm) = 13.77 - 0.27 x GA, the time to beginning of labor (week) = 0.64 + 0.54 x CL (cm). The cases with CL > or = 3.5 cm at 2-3 weeks before labor had a significant higher CS rate than those with CL < or = 3.5 cm (P = 0.002).
  
  
  CONCLUSIONS
  Transvaginal ultrasonographic measurement of CL, CW and the diameter of cervical canal could reflect the maturity of cervix accurately. It could be used as predictors of labor course and outcome of delivery.
authors.affiliation: Peking Union Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing.
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: X
authors.initials: X
authors.lastname: Bian
mesh_terms: D000328:Adult; D000886:Anthropometry; D020070:Cervical Ripening; D002584:Cervix Uteri / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007745:Labor Onset; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D014463:Ultrasonography