What is the most likely diagnosis for a 26-year-old asymptomatic pregnant woman at 30 weeks gestation with a mid-systolic ejection murmur at the right upper sternal border radiating to the carotids and no diastolic murmur?

Physiologic Murmur of Pregnancy

The most likely diagnosis is a physiologic murmur of pregnancy (Option D), as this asymptomatic 26-year-old woman at 30 weeks gestation presents with classic features of a benign flow murmur caused by the hyperdynamic circulatory state of normal pregnancy. 1, 2

Clinical Reasoning

Why This is Physiologic

The presentation is entirely consistent with normal pregnancy cardiovascular changes:

• Soft midsystolic ejection murmur at the left-to-mid sternal border is the most common normal finding in pregnancy, occurring due to the 50% increase in circulating blood volume and increased cardiac output 2
• The patient is completely asymptomatic, which strongly favors a benign etiology 1
• Grade 1-2 midsystolic murmurs in asymptomatic young adults with otherwise normal cardiac examination typically do not require extensive workup 1
• The absence of diastolic murmur is reassuring, as diastolic murmurs are unusual in normal pregnancy and would require further evaluation 2

Why Not Pathologic Aortic Stenosis

While the murmur location (right upper sternal border with carotid radiation) could theoretically suggest aortic stenosis, several factors argue strongly against this:

• Congenital aortic stenosis severe enough to cause a murmur would almost certainly have been diagnosed before age 26, especially in a woman who has reached 30 weeks of pregnancy without symptoms 1
• Significant aortic stenosis causes symptoms during pregnancy due to the fixed cardiac output state being unable to meet increased hemodynamic demands 1
• The ACC/AHA guidelines specifically note that innocent murmurs are especially common in high-output states such as pregnancy 1

Why Not Mitral or Tricuspid Stenosis

• Mitral stenosis produces a diastolic murmur, not a systolic ejection murmur, and this patient has no diastolic component 1
• Tricuspid stenosis is exceedingly rare and also produces a diastolic murmur 1

Management Approach

When Echocardiography is NOT Needed

According to ACC/AHA guidelines, extensive workup is not necessary for grade 1-2 midsystolic murmurs in asymptomatic young adults with otherwise normal cardiac examination and no other physical findings associated with cardiac disease 1

When Echocardiography IS Indicated

Echocardiography would be warranted if any of the following were present:

• Grade 3 or greater intensity murmur 1
• Any diastolic murmur (excluding cervical venous hum or mammary souffle) 1
• Symptoms: dyspnea beyond normal pregnancy, chest pain, syncope, or signs of heart failure 2
• Abnormal dynamic auscultation: murmur intensity increasing with Valsalva or standing, suggesting hypertrophic cardiomyopathy or mitral valve prolapse 1
• Other abnormal cardiac findings: widely split S2, systolic ejection sounds, or specific physiological maneuver responses 1

Common Pitfalls to Avoid

• Do not order unnecessary echocardiography in asymptomatic pregnant women with soft systolic murmurs, as research demonstrates that echocardiography does not substantially alter antenatal management in the absence of other clinical or ECG abnormalities 3
• Do not confuse normal pregnancy findings with pathology: louder S1 with prominent splitting, physiologically split S2, S3 gallops, and hyperkinetic precordial impulse are all normal in pregnancy 2
• Do not dismiss a murmur if the patient becomes symptomatic or if the murmur characteristics change, as this would warrant immediate reassessment 2

Expected Normal Findings in Pregnancy

The ACC/AHA guidelines describe the following as normal cardiovascular examination findings in pregnancy:

• Soft grade 1-2 midsystolic murmur at mid-to-upper left sternal edge 2
• Continuous murmurs (venous hum or mammary souffle) 2
• Third heart sound (S3) present in most patients 2
• Louder first heart sound with prominent splitting 2
• Hyperkinetic precordial impulse 2