Studies of malformations in monozygotic twins are important in elucidating the roles played by genetic and environment al factors in the development of these malformations.
We report on monozygotic twins with cleft submucousal palate, one of whom had ventricular septal defect. Because of differences in the severity of cleft palate, birth weight, and the heart defect, processes such as twin-twin transfusion may have played a part in the phenotypic differences.
