Hypoplastic left heart syndrome occurs in up to four out of every 10,000 live births. The syndrome comprises 8 percent of all cases of congenital heart disease. It is one of the top three heart abnormalities to cause problems in the newborn.... HLHS occurs slightly more often in boys (55% -70%) than in girls. In many children, HLHS occurs by chance, with no clear reason evident for the underdevelopment. However, the rate of occurance is increased in patients with Turner, Noonan, Smith-Lemli-Opitz or Holt-Oram Syndromes. Certain chromosomal duplications, translocations and deletions have been associated with HLHS, but not in most cases. Babies with this condition may appear normal at birth. Fetuses are nourished by oxygen-rich blood from their mothers so they don't breathe and don't use their lungs. Babies with hypoplastic left heart syndrome may seem normal at birth because the patent ductus arteriosus (a blood vessel that connects the pulmonary artery to the aorta, thereby bypassing the lungs and the defective left side of the heart.) is still open, allowing blood to continue circulating directly into the aorta and out to the rest of the body. Once the ductus closes a few days after birth, blood flows to the lungs and then to the left side of the heart where it is blocked and can't circulate through the rest of the body. It is at this time that these babies show symptoms. My daughter was born with this and died from it xxx