Aims: To review the course of monochorionic (MC) twin gestations in which one or both fetuses were diagnosed with congenital heart disease (CHD) and to identify clinical characteristics regarding the related intrauterine environmental factors particularly associated with non-twin-twin transfusion syndrome (TTTS). Methods: This study is a review of a two-center experience of MC twin pregnancies with CHD born between 2000 and 2006. Results: There were 87 MC twin pregnancies of which 11 were associated with fetal heart disease. We found concordance of CHD in 2 of the 11 twin sets. Among all of the discordant cases, the size of the affected twin was smaller. TTTS was observed in one case associated with CHD; in this case the donor twin had a coarctation of the aorta. Abnormal cord insertion was observed in 9 (69%) out of the 13 affected infants, and a significant relation was found between the presence of CHD and abnormal cord insertion. Conclusions: Of the MC twins, the smaller seemed more likely to be affected by primary structural cardiac anomalies. CHD in MC twins is possibly related to an abnormal cord insertion. Further studies are warranted to determine whether a causal relationship exists.
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