title: Fetal hypertension and abnormal Doppler velocimetry in an ovine model of intrauterine growth restriction.
abstract: OBJECTIVE
  Our objective was to test the hypothesis that systemic blood pressure (BP) is increased above normal in intrauterine growth restricted (IUGR) fetal lambs with elevated umbilical artery (UmA) Doppler indices.
  
  
  METHODS
  Five pregnant ewes were exposed to hyperthermic conditions for 80 days beginning at 40 days' gestation (dGA) to induce IUGR. They were then placed in ambient conditions with 6 additional ewes that served as controls. Doppler indices were calculated from UmA Doppler flow velocity waveforms. At 128 dGA, fetal catheters were placed for measurement of umbilical blood flow (UBF) by an ethyl alcohol steady-state diffusion technique and for aortic BP measurements. At 132 dGA, fetal mean systemic BP and blood flow were determined. At necropsy the placental and fetal weights were recorded. UBF was normalized for fetal weight. Linear regression, F tests and t tests were performed as appropriate. P < .05 was considered significant.
  
  
  RESULTS
  Compared with control pregnancies, the IUGR pregnancies showed: (1) reduced fetal and placental weights, (2) elevated systemic BP, (3) reduced UBF, (4) elevated UmA and aortic Doppler velocimetry indices, (5) increased resistance per 100 g placenta, and (6) decreased UmA oxygenation and increased lactic academia. The UmA Doppler index of resistance (systolic/diastolic ratio) correlated strongly with calculated resistance (R2 = 0.7). Doppler indices also correlated with systemic BP (R2 = 0.5).
  
  
  CONCLUSIONS
  Ovine IUGR fetuses with high UmA Doppler indices have elevated systemic BPs. UmA Doppler indices of resistance correlate well with (1) fetal systemic BPs and (2) resistance as calculated by pressure/flow. This whole animal study shows that IUGR fetuses are hypertensive and that increased UmA Doppler resistance indices are consistent with a fetal-placental hypertensive state.
authors.affiliation: Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center, Denver, Colo, USA. Henry.Galan@uchsc.edu
authors.forename: Henry L
authors.initials: HL
authors.lastname: Galan
authors.forename: Russell V
authors.initials: RV
authors.lastname: Anthony
authors.forename: Serena
authors.initials: S
authors.lastname: Rigano
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Parker
authors.forename: Barbara
authors.initials: B
authors.lastname: de Vrijer
authors.forename: Enrico
authors.initials: E
authors.lastname: Ferrazzi
authors.forename: Randall B
authors.initials: RB
authors.lastname: Wilkening
authors.forename: Timothy R H
authors.initials: TR
authors.lastname: Regnault
mesh_terms: D000818:Animals; D001794:Blood Pressure; D004195:Disease Models, Animal; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D005333:Fetus / Q000098:blood supply; D006973:Hypertension / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D012756:Sheep; D014469:Umbilical Arteries / Q000503:physiopathology*