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.