Cardiovascular Changes in Pregnancy

Pregnancy shifts the maternal circulation into a high-output state to support both maternal tissue demands and uteroplacental perfusion. Vasodilation lowers systemic vascular resistance, while increased blood volume, heart rate, and stroke volume raise cardiac output. These changes explain why a healthy pregnant patient may have a faster pulse, a benign systolic flow murmur, mild dependent edema, or an S3 without heart failure. The clinical challenge is recognizing when a finding no longer fits that expected pattern. Gradual, stable changes that match gestational timing are different from abrupt dyspnea, syncope, chest pain, pulmonary edema, or objective ventricular dysfunction. Assess the patient against her prepregnancy baseline, the expected trajectory of pregnancy, and the presence or absence of impaired perfusion. The normal adaptations that follow provide the baseline for making that distinction.