title: Prenatal evaluation of the conus medullaris position in normal fetuses and fetuses with spina bifida occulta using three-dimensional ultrasonography.
abstract: OBJECTIVE
  This study aimed to assess the fetal conus medullaris (CM) position with three-dimensional (3D) ultrasonography and its use in detecting and diagnosing spina bifida occulta (SBO).
  
  
  METHODS
  We examined 150 normal fetuses (gestational age, 20-38 weeks) and 14 fetuses with SBO. All fetuses underwent prenatal 3D ultrasonography, and the CM position in relation to the vertebral body was evaluated using volume contrast imaging. Intra- and inter-observer agreements were assessed using weighted kappa. The correlation between gestational age and CM level was determined by linear regression analysis.
  
  
  RESULTS
  Operators successfully located the CM position in 145 cases. The CM was at L3 or higher in all normal group cases. A linear relationship was noted between gestational age (X) and CM position (Y) (Y = 0.118X + 6.011, R(2)  = 0.679, P < 0.001). The weighted kappa values for intra- and inter-observer agreement were 1.0 and 0.788, respectively. The CM was located at L3 in one case and lower than L3 in 13 cases in the SBO group. All values were below the fifth percentile for the normal group.
  
  
  CONCLUSIONS
  Three-dimensional ultrasonography may accurately determine the CM vertebral level. Prenatal evaluation of the CM position may improve the detection and diagnosis of SBO.
authors.affiliation: Department of Ultrasonic Medicine, Fetal Medical Centre, the First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Lei
authors.forename: Hong-Ning
authors.initials: HN
authors.lastname: Xie
authors.forename: Ju
authors.initials: J
authors.lastname: Zheng
authors.forename: Jie-Ling
authors.initials: JL
authors.lastname: Feng
authors.forename: Liu
authors.initials: L
authors.lastname: Du
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D005333:Fetus / Q000473:pathology; D005865:Gestational Age; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D016136:Spina Bifida Occulta / Q000000981:diagnostic imaging*; D013116:Spinal Cord / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult