Physiologic changes of pregnancy

Arterial compliance increases throughout pregnancy
Cardiac output begins to increase by 5 weeks and plateaus at 20 weeks
Heart rate increases throughout pregnancy
Systolic blood pressure increases at 20 weeks
Systemic vascular resistance decreases early on, continues to decrease, and plateaus toward the end of pregnancy
Stroke volume peaks at 24 weeks
Relative anemia: Red blood cell mass increases but relatively less than plasma volume, which expands by 10% to 15% by 6–12 weeks
During labor: Cardiac output increases 15% to 50% with contractions, and circulating volume increases