Is It Normal to Have a Heart Murmur During Pregnancy?
Yes, it is completely normal to develop a heart murmur during pregnancy—soft systolic murmurs occur in over 90% of pregnant women and are typically benign, physiologic findings related to the increased blood volume and cardiac output of pregnancy. 1, 2
Why Pregnancy Causes Heart Murmurs
Pregnancy induces dramatic cardiovascular changes that commonly produce audible murmurs:
- Blood volume increases by 40-50% and cardiac output rises proportionally, peaking in the second and third trimesters 1, 3
- Heart rate increases by 10-20 beats per minute 1
- Systemic vascular resistance falls, causing a widened pulse pressure 1
These hemodynamic changes create turbulent blood flow across normal heart valves, producing the characteristic "flow murmurs" of pregnancy.
What a Normal Pregnancy Murmur Sounds Like
A physiologic pregnancy murmur is typically a soft (grade 1-2 out of 6), midsystolic murmur best heard along the mid to upper left sternal edge. 1, 2, 4 Additional normal findings include:
- Third heart sounds in 80% of pregnant women 4
- Continuous murmurs (venous hum or mammary souffle) that can be obliterated with positional changes or pressure 1, 2
- The mammary souffle appears in late pregnancy or early postpartum, heard over engorged breasts, and disappears when standing 1
Critical Red Flags: When a Murmur Is NOT Normal
Diastolic murmurs are unusual in pregnancy and warrant immediate evaluation. 1, 2, 5, 6 You must refer urgently if any of these features are present:
- Any diastolic murmur (these are rarely physiologic)
- Loud or harsh murmurs (grade 3/6 or higher)
- Holosystolic murmurs
- Murmurs radiating to the back or neck
- Associated symptoms: paroxysmal nocturnal dyspnea, syncope (not just presyncope), anginal chest pain, or progressive dyspnea beyond normal pregnancy 5, 6
- Signs of heart failure: pulmonary crackles (rare in normal pregnancy), anasarca, or significant jugular venous distention 7, 5
Important Nuances About Pregnancy and Murmurs
The increased cardiac output can accentuate murmurs from stenotic lesions (mitral stenosis, aortic stenosis) making them more prominent 1, 2, 4. Conversely, murmurs from regurgitant lesions (aortic regurgitation, mitral regurgitation) may actually decrease or become inaudible due to the fall in systemic vascular resistance 1, 2, 4.
Women with hypertrophic cardiomyopathy and outflow tract gradients are especially likely to be first diagnosed during pregnancy when their murmurs become more apparent 8.
When to Order an Echocardiogram
Echocardiography is NOT routinely needed for soft systolic murmurs in asymptomatic pregnant women with normal physical capacity and no other concerning findings. 9 A study of 50 pregnant women referred for newly discovered murmurs found that echocardiography did not substantially alter management in the absence of other clinical or ECG abnormalities 9.
Order echocardiography if:
- Any diastolic murmur is present
- The systolic murmur is loud (≥3/6), harsh, or holosystolic
- Symptoms suggest cardiac disease (not just normal pregnancy dyspnea)
- History of prior cardiac disease or family history of cardiomyopathy
- Abnormal ECG findings
Common Pitfall to Avoid
Do not confuse normal pregnancy dyspnea on exertion with heart failure. Mild exertional dyspnea and the sensation of being unable to take a deep breath are extremely common in normal pregnancy 7, 5. However, progressive dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and recumbent cough indicate heart failure and require urgent evaluation 7.
Bottom Line for Clinical Practice
Reassure your patient that a soft systolic murmur discovered during pregnancy is almost certainly a normal physiologic finding related to increased blood flow. Document the murmur characteristics carefully. If the murmur is soft (grade 1-2), systolic, without radiation, and the patient is asymptomatic with normal exercise tolerance, no further workup is needed—just routine prenatal care. Any concerning features warrant prompt referral to cardiology or a specialized pregnancy and heart disease clinic.