Table 33: Hemodynamic changes in normal pregnancy
Parameter: Blood volume

First: Rises

Second: Rises

Third: Maximum at 45%-50% early on, additional 33% increase in twin gestation

Peripartum: Potential rapid auto-transfusion from placenta due to sympathetic stimulation and uterine contraction
Parameter: Peripheral vascular resistance and blood pressure

First: Gradual drop, diastolic more such that pulse pressure increases

Second: At lowest point in mid pregnancy

Third: Gradual reversion to normal

Peripartum: Variable changes depending on stage and sympathetic stimulation
Parameter: Heart rate

First: Increases

Second: Peaks at 20% late

Third: 20% increase

Peripartum: Further increase
Parameter: Cardiac output

First: Increases

Second: Increases

Third: Maximal 30%-50% increase early

Peripartum: Further increase up to 31% in labour, 49% in second stage. Return to 3rd trimester values within 1 h of delivery