title: Maternal middle cerebral artery blood flow velocity variation with gestational age.
abstract: OBJECTIVE
  To assess the variation of the maternal middle cerebral artery blood flow velocity with gestational age in a normotensive pregnant population.
  
  
  METHODS
  Middle cerebral artery blood flow velocity was assessed transcranially in 154 normotensive pregnant women using a 2-MHz pulsed probe. We assessed maximum systolic, minimum diastolic, and mean velocity and resistance index. Subjects were classified into seven gestational age categories of 4-week intervals starting from 13 weeks. Analysis of variance was used to indicate a significant difference in cerebral blood flow velocity with gestational age, and Tukey test to assess the significance.
  
  
  RESULTS
  Maximum systolic velocity fell significantly in the third trimester (P < .01) to the lowest value (62 cm/second). Minimum diastolic velocity did not change with gestational age (28 cm/second). Mean velocity fell significantly from 25-36 weeks.
  
  
  CONCLUSIONS
  Systolic and mean maternal middle cerebral artery blood flow velocity fell significantly with advancing gestational age, even though diastolic velocity did not vary. These changes did not correlate with mean arterial pressure changes with gestational age.
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Williams
authors.forename: S
authors.initials: S
authors.lastname: Wilson
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000502:physiology*; D012016:Reference Values; D017585:Ultrasonography, Doppler, Transcranial