V1v: Physiological consequences of supine position in pregnancy


  • Overall increase in CO, SV, HR to accommodate physiological changes of pregnancy
  • Supine position reduces CO with almost complete occlusion IVC & lateral displacement of subrenal aorta when supine due to compression by pregnant uterus
  • Improves with L) lateral position which displays the greatest CO & SV

Aortocaval Compression Syndrome

  • Compression of Aorta & IVC by pregnant uterus
  • Reduction in CO
  • Compensation by sympathetic activation
  • Pallor, dizziness, hypotension, diaphoresis, nausea & LOC
  • Resolution w L) lateral tilt


  • Narrowing of upper airway by 3rd trimester
  • OSA & snoring when supine
  • Marked reduction in FRC 70% !


  • Complete IVC occlusion at level of renal vein entry
  • Increase in renal venous pressure
  • Oliguria


  • Lower back pain