Cardiovascular Changes in Pregnancy

Pregnancy converts the maternal circulation into a higher-flow, lower-resistance system. Plasma expands, the heart pumps more blood, and systemic vascular resistance falls so that uteroplacental blood flow can increase. Those adaptations are beneficial when the patient is upright and compensating; they become hazardous when a gravid uterus obstructs venous return, blood pressure rises, clotting is activated, or the heart cannot meet the increased workload. The bedside question is not whether a finding is different from the non-pregnant state. It is whether the finding fits the expected pattern, whether perfusion is being maintained, and whether a dangerous transition is occurring. The largest haemodynamic shifts occur during labour and the first hours after birth, so a stable antenatal assessment does not eliminate postpartum cardiovascular risk.