title: Effect of orthostatic stress on umbilical Doppler waveforms in normal and hypertensive pregnancies.
abstract: OBJECTIVE
  Our study examined the effects of orthostatic stress and maternal hemodynamics on umbilical systolic/diastolic ratios in normal and hypertensive pregnancies.
  
  
  METHODS
  Eighteen normal and 20 hypertensive third-trimester pregnancies were examined in the left lateral recumbent, sitting, and standing positions. Measurements included umbilical systolic/diastolic ratio, maternal blood pressure, maternal cardiac output, and maternal total peripheral resistance.
  
  
  RESULTS
  All patients demonstrated a fall in cardiac output and a rise in total peripheral resistance with standing. No change in systolic/diastolic ratio occurred with change to the upright position in patients with normotension. Patients with hypertension exhibited a significant increase in umbilical systolic/diastolic ratio with postural change. The increase was more marked in women who had hypertension with elevated peripheral resistance.
  
  
  CONCLUSIONS
  Patients with hypertension are at increased risk of elevation of systolic/diastolic ratio with postural change; women with high-resistance hypertension may be at highest risk.
authors.affiliation: Department of Obstetrics and Gynecology, University of Washington Medical Center, Seattle.
authors.forename: T K
authors.initials: TK
authors.lastname: Sorensen
authors.forename: S
authors.initials: S
authors.lastname: Hendricks
authors.forename: T R
authors.initials: TR
authors.lastname: Easterling
authors.forename: K L
authors.initials: KL
authors.lastname: Carlson
authors.forename: T J
authors.initials: TJ
authors.lastname: Benedetti
mesh_terms: D003971:Diastole; D005260:Female; D005333:Fetus / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011187:Posture; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular; D012016:Reference Values; D013599:Systole; D016216:Ultrasonography, Prenatal; D014470:Umbilical Cord / Q000098:blood supply* / Q000000981:diagnostic imaging; D014655:Vascular Resistance