Down's syndrome: different distribution of congenital heart diseases between the sexes

We have investigated the reasons why female patients with Down's syndrome prevail in our out-patient clinic for Paediatric Cardiology compared to the higher incidence of Down's syndrome among live born male children. We reviewed 277 cases of Down's syndrome, 119 males (42.96%) and 158 females (57.04%) from 1970 to 1987. A final diagnosis of the type of the congenital heart disease was accomplished among 210 cases, 85 males (40.47%) and 125 females (59.38%). This different distribution between the sexes was significant (P less than 0.01) when compared to that of the general population with congenital heart disease (4150 patients, 2108 males and 2042 females). The dominant lesion was atrioventricular septal defect, (130 cases; 46 males [54.11%] and 84 females [67.20%]). We found an identical incidence of this lesion among patients without Down's syndrome. In the studied population, we did not find any of the congenital heart diseases usually prevalent in males, such as aortic coarctation or stenosis and complete transposition. The molecular determinants of Down's syndrome seem to influence the preponderance of atrioventricular septal defect in females, increasing its incidence, while seeming to act in a negative way concerning congenital heart diseases usually showing male prevalence.