title: Cardiovascular and endocrine effects of a single course of maternal dexamethasone treatment in preterm fetal sheep.
abstract: OBJECTIVE
  To determine the effects of a single course of maternally administered dexamethasone on preterm fetal sheep in utero.
  
  
  METHODS
  Prospective randomised controlled trial.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  Pregnant sheep at 0.7 of gestation.
  
  
  METHODS
  Pregnant ewes at 103 days of pregnancy (term = 147 days) were given two intramuscular injections of vehicle (n= 7) or 12 mg of dexamethasone (DEX; n= 8) 24 hours apart. Fetuses were continuously monitored for five days.
  
  
  METHODS
  Fetal mean arterial blood pressure, carotid and femoral arterial blood flow and vascular resistance, heart rate, heart rate variability, fetal plasma cortisol and ACTH and fetal body movements.
  
  
  RESULTS
  DEX injections led to an acute increase in mean arterial blood pressure with a rise in carotid and femoral vascular resistance, a fall in femoral arterial blood flow, and a brief fall in fetal heart rate followed by significant tachycardia. From 24 hours after the injections, mean arterial blood pressure and vascular resistance returned to control values, however, a mild tachycardia [200 (3) vs 184 (4) bpm, P < 0.05] and loss of the circadian pattern of fetal heart rate variability persisted until the end of recording. Plasma ACTH and cortisol were markedly suppressed by DEX (P < 0.05), with values returning to control levels 32 and 72 hours after the first injection, respectively. There was no effect on basal fetal heart rate variability, body movements, carotid arterial blood flow, or the circadian pattern of fetal heart rate.
  
  
  CONCLUSIONS
  In contrast to previous experiments utilising direct fetal infusion of steroids, maternal administration of DEX was associated with only transient hypertension.
authors.affiliation: Department of Physiology, The University of Auckland, New Zealand.
authors.forename: Josine S
authors.initials: JS
authors.lastname: Quaedackers
authors.forename: Vincent
authors.initials: V
authors.lastname: Roelfsema
authors.forename: Mhoyra
authors.initials: M
authors.lastname: Fraser
authors.forename: Alistair J
authors.initials: AJ
authors.lastname: Gunn
authors.forename: Laura
authors.initials: L
authors.lastname: Bennet
mesh_terms: D000302:Adrenal Cortex / Q000187:drug effects*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000502:physiology; D005324:Fetal Movement / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D006340:Heart Rate, Fetal / Q000187:drug effects; D006854:Hydrocortisone / Q000378:metabolism; D007273:Injections, Intramuscular; D007752:Obstetric Labor, Premature / Q000503:physiopathology*; D011247:Pregnancy; D011897:Random Allocation; D012756:Sheep; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone