title: Doppler analysis of the umbilical artery: why we must prefer the free loop of the cord.
abstract: OBJECTIVE
  The main objective was to confirm with modern tools the former assertion that there is a vascular resistance gradient along the umbilical cord.
  
  
  METHODS
  We performed a prospective observational study in a population of women with third trimester monofetal and uncomplicated pregnancies during two months. Pulsatility Index and Resistance Index were calculated on three sites: placental end, free loop and fetal end of the cord.
  
  
  RESULTS
  Sixty-five pregnant women were included in the study. Mean gestational age was 32 weeks and 3 days. We confirmed the presence of a resistance gradient with a significant increase of both Resistance and Pulsatility Indices from the placental toward the fetal end of the cord (Resistance Index = 0.61±0.07 at placental end and 0.66±0.11 at fetal end [P<0.001]. Pulsatility Index = 0.97±0.17 at placental end, and 1.06±0.25 at fetal end [P<0.001]).
  
  
  CONCLUSIONS
  Resistances seem higher when doppler waveform analysis of the umibilical artery are performed at the fetal end of the cord. We recommend the free loop insonation site to obtain a better sensitivity. International guidelines strongly need to be well diffused in order to standardize practices.
authors.affiliation: Department of Gynecology and Obstetrics, Hôpital Tenon, Assistance Publique des Hôpitaux de Paris Université Pierre et Marie Curie Paris 6, France - drcohenjonathan@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Cohen
authors.forename: M J
authors.initials: MJ
authors.lastname: Wauquiez
authors.forename: J
authors.initials: J
authors.lastname: Janse-Marec
mesh_terms: D000328:Adult; D005260:Female; D005865:Gestational Age; D006801:Humans; D010920:Placenta / Q000098:blood supply / Q000000981:diagnostic imaging; D011247:Pregnancy; D011446:Prospective Studies; D011673:Pulsatile Flow; D012680:Sensitivity and Specificity; D018608:Ultrasonography, Doppler / Q000379:methods*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014469:Umbilical Arteries / Q000000981:diagnostic imaging*; D014470:Umbilical Cord / Q000098:blood supply* / Q000000981:diagnostic imaging; D014655:Vascular Resistance / Q000502:physiology