TABLE 5.
Hemodynamic changes in normal pregnancy
| Parameter |
Trimester |
Peripartum | ||
|---|---|---|---|---|
| First | Second | Third | ||
| Blood volume | Rises | Rises | Maximum at 45%–50% early on, additional 33% increase in twin gestation | Potential rapid autotransfusion from placenta due to sympathetic stimulation and uterine contraction |
| Peripheral vascular resistance and blood pressure | Gradual drop, diastolic more such that pulse pressure increases | At lowest point in mid pregnancy | Gradual reversion to normal | Variable changes depending on stage and sympathetic stimulation |
| Heart rate | Increases | Peaks at 20% increase late | 20% increase | Further increase |
| Cardiac output | Increases | Increases | Maximal 30%–50% increase early | Further increase up to 31% in labour, 49% in second stage. Return to 3rd trimester values within 1 h of delivery |