title: External cephalic version induced fetal cerebral and umbilical blood flow changes are related to the amount of pressure exerted.
abstract: OBJECTIVE
  To correlate the applied pressure during external cephalic version with the changes in fetal middle cerebral arterial and umbilical arterial flow before and after the procedure.
  
  
  METHODS
  A prospective observational study over a two-year period.
  
  
  METHODS
  External cephalic version was performed in a university hospital.
  
  
  METHODS
  Sixty-nine women with singleton breech-presenting pregnancy at or above 36 weeks of gestation undergoing external cephalic version.
  
  
  METHODS
  During external cephalic version, the operator wore a pair of pressure-sensing gloves which had thin piezo-resistive sensors positioned on the palmar surface. During each version procedure, real-time pressure readings were recorded from all sensors, and then analysed with a computer program. The amount of pressure applied over time was presented by pressure-time integral. The pulsatility indices of both fetal middle cerebral artery and umbilical artery before and after external cephalic version were measured. The changes of pulsatility indices of both middle cerebral artery and umbilical artery were presented as a ratio of the post-external cephalic version pulsatility indices to pre-external cephalic version pulsatility indices, denoted by middle cerebral artery pulsatility index ratio and umbilical artery pulsatility index ratio, respectively. The statistical correlation between pressure-time integral and middle cerebral artery pulsatility index ratio and umbilical artery pulsatility index ratio are analysed using Pearson's correlation test.
  
  
  METHODS
  Changes in pulsatility indices of fetal middle cerebral and umbilical arteries and fetal heart rate after external cephalic version.
  
  
  RESULTS
  The overall success rate of external cephalic version was 77%. There was a significant negative correlation between pressure-time integral and both middle cerebral artery pulsatility index ratio (P= 0.001) and umbilical artery pulsatility index ratio (P= 0.012). When women were categorised according to placental site, pressure-time integral was negatively correlated with middle cerebral artery pulsatility index ratio only when the placenta was posteriorly located (P= 0.003), and with umbilical artery pulsatility index ratio only when the placenta was laterally located (P= 0.03).
  
  
  CONCLUSIONS
  The greater the force applied during external cephalic version, the greater the reduction in pulsatility indices of middle cerebral artery and umbilical artery, indicating an increase in blood flow through these arteries. The increase in cerebral blood flow after external cephalic version is more prominent when the placenta is lying posteriorly, while the increase in umbilical flow is more prominent when the placenta is lying laterally. These findings suggest that the vascular changes probably represent a direct effect of force exerted on the fetal head and the placenta.
authors.affiliation: Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Tak Yeung
authors.initials: TY
authors.lastname: Leung
authors.forename: Daljit Singh
authors.initials: DS
authors.lastname: Sahota
authors.forename: Wing Yee
authors.initials: WY
authors.lastname: Fok
authors.forename: Lin Wai
authors.initials: LW
authors.lastname: Chan
authors.forename: Tze Kin
authors.initials: TK
authors.lastname: Lau
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003020:Clothing; D005260:Female; D005865:Gestational Age; D006801:Humans; D020768:Middle Cerebral Artery / Q000502:physiology*; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D011312:Pressure; D011446:Prospective Studies; D014469:Umbilical Arteries / Q000502:physiology*; D014710:Version, Fetal