In summary:

Circulatory Changes in Pregnancy
Heart rate Increased (from 75 to 85-90)
Stroke volume Increased (from 65ml to 80-90ml)
Cardiac output Increased (from 5L/min to 7L/min)
Blood pressure Decreased
   
Systemic vascular resistance Decreased
Pulmonary vascular resistance Decreased
Pulmonary artery wedge pressure Unchanged
Blood volume Increased by 50%
CVP Unchanged
Colloid oncotic pressure Decreased
  • Albumin and oncotic pressure decrease gradually thoughout pregnancy
  • Oxygen consumption increases by 20% during pregnancy
  • FRC decreases during pregnancy, due to compression of the diaphragm by the gravid uterus.
  • Blood pressure decreases and is lowest in the second trimester
  • Heart rate increases gradually thoughout pregnancy
  • Stroke volume increases gradually thoughout pregnancy
  • Cardiac output increases gradually thoughout pregnancy
    • however, the IVC is compressed by the gravid uterus in the supine position, decreasing the preload
  • Systemic vascular resistance decreases gradually thoughout pregnancy
  • Total blood volume increases gradually during pregnancy

References

Oh's Intensive Care manual:

Chapter 64   (pp. 684) General  obstetric  emergencies by Winnie  TP  Wan  and  Tony  Gin

Chapter 65   (pp. 692) Severe  pre-existing  disease  in  pregnancy by Jeremy  P  Campbell  and  Steve  M  Yentis

Thornburg, Kent L., et al. "Hemodynamic changes in pregnancy." Seminars in perinatology. Vol. 24. No. 1. WB Saunders, 2000.