Background: Congenital heart disease (CHD) is the most common malformation in the fetal and neonatal period but little is known about its cause. The distribution analysis of CHD in dizygotic twins could provide a useful tool to evaluate the role of genetic and environmental factors in the development of CHD. Dizygotic twins are siblings with different genes, growing together in the same womb.
Aim of study: To investigate the occurrence of CHD in a large sample of dizygotic twins of nonconsanguineous healthy parents, comparing the data from non-twin patients.
Methods: From January 1999 to December 2002, we enrolled 1743 CHD patients with, at least 1 sibling, and 66 pairs of dizygotic twins, referred to our tertiary center. The diagnosis of CHD was based on clinical and echocardiographic evaluation.
Results: Considering only the sibling nearest in age for each non-twin patient the recurrence was 67/1743 (3.8%). Among these 67 patients, 35 (52.2%) had a sibling with the same or similar CHD. Conversely, considering all 1886 siblings, recurrence of CHD in the non-twin group was 70/1743 (4%). Of the 70 patients, 36 (36/70, 51.4%) had a sibling with the same suspected pathogenic mechanism of CHD. In 9/66 pairs of twins (13.6%), both siblings had a CHD. In the nine pairs of twins in whom both siblings had a CHD, the percentage of concordance (based on the suspected pathogenic mechanism) for CHD was 100% (p<0.05).
Conclusions: Our findings suggest that the higher recurrence and concordance of CHD found in dizygotic twins could depend on some poorly identified environmental risk during the pregnancy.