title: Evaluation of antenatal umbilical coiling index at 16-21 weeks of gestation as a predictor of trisomy 21 and other chromosomal defects.
abstract: OBJECTIVE
  To determine whether there is an association between sonographically assessed hyper- or hypocoiling of the umbilical cord and the presence of trisomy 21, to provide reference values for the antenatal umbilical coiling index (aUCI) at a gestational age of 16-21 weeks and to determine whether these measurements are reliable and reproducible.
  
  
  METHODS
  This was a prospective study of 737 pregnancies in which the aUCI was measured between 16 and 21 weeks of gestation by ultrasound at the time of amniocentesis. The aUCI was calculated as the reciprocal value of the mean length of one complete coil in centimeters. We created reference curves and studied the relationship with trisomy 21 and other chromosomal defects. In 30 pregnancies we studied the intra- and interobserver variation in measurements using Bland-Altman plots with associated 95% limits of agreement and intraclass correlation coefficients.
  
  
  RESULTS
  aUCI was found to be non-linearly related to gestational age at 16-21 weeks and reference curves were created for the mean aUCI and the 2.3(rd) , 10(th) , 90(th) and 97.7(th) percentiles. There was no significant difference in aUCI values between the reference group (n = 714) and cases with trisomy 21 (n = 16) or other aneuploidies (n = 7) (one-way ANOVA, P = 0.716). There was good intra- and interobserver agreement in aUCI measurements.
  
  
  CONCLUSIONS
  The aUCI can be measured reliably and varies according to gestational age at 16-21 weeks. The aUCI was not significantly associated with trisomy 21 or other chromosomal defects.
authors: Department of Obstetrics, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: C P M
authors: CP
authors: Verkleij
authors: A C C
authors: AC
authors: van Oppen
authors: E J H
authors: EJ
authors: Mulder
authors: M W M
authors: MW
authors: de Laat
authors: E
authors: E
authors: Sikkel
authors: M P H
authors: MP
authors: Koster
authors: I
authors: I
authors: van der Tweel
authors: A
authors: A
authors: Franx
authors: G H A
authors: GH
authors: Visser
mesh_terms: D000328:Adult; D025063:Chromosome Disorders / Q000000981:diagnostic imaging; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal; D014470:Umbilical Cord / Q000033:anatomy & histology / Q000000981:diagnostic imaging*
keywords: Down syndrome; aneuploidies; observer; sonography; trisomy 21; umbilical coiling index; umbilical cord