Co-occurrence of coarctation of the aorta and hypospadias in smaller twins in monochorionic pregnancies: two case reports.

We reconstructed of the aortic arches of two unrelated boys, who were the smaller twin in monochorionic pregnancies, because they had coarctation of the aorta (CoA). They both had hypospadias. The co-twins, the larger twins, had neither CoA nor hypospadias. Although CoA and hypospadias both have been associated separately with monozygotic pregnancy, this is the first report of CoA and hypospadias occurring together. These cases indicate that epigenetic factors such as unbalanced fetal circulation in monochorionic pregnancy may be involved in co-occurrence of CoA and hypospadias.