Congenital heart defects in a large, unselected cohort of monochorionic twins

OBJECTIVE: To determine the prevalence of congenital heart defects (CHDs) in a large, unselected cohort of monochorionic (MC) twins. STUDY DESIGN: We completed a chart review of all MC twin pregnancies in the Kaiser Permanente Northern California population from 1996 to 2003. CHDs were identified by diagnostic codes and confirmed by postnatal echocardiograms. Follow-up was obtained through one year of age. RESULT: A total of 926 liveborn MC twins met inclusion criteria. The prevalence of CHDs was 7.5%, 11.6 times the general population rate (CI 9.2 to 14.5). Septal defects were most common. 20% of infants with heart defects had twin-to-twin transfusion syndrome (TTTS) versus 8% of infants without defects (P<0.01); this association remained significant when controlling for potential confounders. CONCLUSION: The prevalence of CHDs in this large cohort of MC twins was significantly higher than the general population rate, with TTTS an added risk factor.