We report on two prenatal ultrasound diagnoses of left ventricular 
non-compaction cardiomyopathy (LVNC) associated with mutation of the cardiac 
β-myosin heavy chain gene (MYH7). LVNC is characterized by a trabecular meshwork 
and deep intertrabecular myocardial recesses communicating with the left 
ventricular cavity. Clinical features range from non-penetrant disease in adult 
carriers to heart failure, arrhythmia and thromboembolism. Both cases showed 
cardiomegaly on prenatal ultrasound examinations, with features indicating 
non-compaction of the myocardium apparent in the third trimester. Mutations in 
the MYH7 gene were identified postnatally in each case in both the proband and 
the father. One infant underwent surgical mitral valvuloplasty and a mechanical 
valve implant later; in the other, left ventricular function was unimpaired at 
birth. Cardiac function in both cases remained stable at last follow-up. These 
cases highlight the importance of prenatal ultrasound diagnosis of LVNC and the 
need for cardiologic and molecular testing of first-degree relatives who may be 
unknown carriers of an MYH7 mutation.