Cardiac hypertrophy of one fetus and selective growth restriction of the other fetus in a monochorionic twin pregnancy.

Cardiac hypertrophy in the recipient fetus of twin-twin transfusion syndrome (TTTS) has been reported previously. We encountered an unusual set of monochorionic twins in which one twin had cardiac hypertrophy without TTTS while the other fetus had selective growth restriction. In this case, the diagnosis of selective growth restriction was made at 17 weeks of gestation, and right ventricular hypertrophy was identified in the co-twin at 21 weeks; however, no signs of TTTS were observed. At 29 weeks we concluded that the fetal circulation had deteriorated based on echocardiographic findings that included hydrops fetalis and an elevated preload index. Emergency cesarean section was performed. Our experience suggests that hypertrophic cardiomyopathy-like change in a monochorionic twin pregnancy may arise in settings outside of TTTS, including growth restriction of a co-twin. We believe our case will assist the discussion surrounding the etiology of cardiac hypertrophy in monochorionic twins.