Objectives: This study was performed to determine risk factors for cerebral palsy (CP) in monochorionic twins, especially with twin-to-twin transfusion syndrome (TTTS). Methods: In 33 pathologically confirmed monochorionic pregnancies, we analyzed the incidence of cardiovascular and neurological complications. Results: Seventeen cases were diagnosed as TTTS. Myocardial hypertrophy was detected in seven recipient twins of TTTS, but not found in the donor twins of TTTS or in non-TTTS. CP developed in six out of 29 in TTTS and one out of 32 in non-TTTS. In TTTS, all the cases with CP were seen in the recipient twins. The development of CP was significantly associated with cardiovascular complications such as myocardial hypertrophy and hydropic changes. Conclusions: Myocardial hypertrophy found in the recipient twins in TTTS seems to be a risk for developing CP later on, which may have implications in understanding the pathogenesis of CP.