Survival depends on the type and extent of joining and on the presence or absence of associated anomalies. In the absence of severe anomalies, thoracoomphalopagus twins have a reasonable chance of survival after surgical separation. Prognosis is usually determined by the extent of fusion of the heart, but as noted above, surgical separation is usually deferred for weeks or months. In a review of 47 pairs of surgically separated thoracopagus twins, Chiu et al. reported an overall survival rate of 48 percent. However, the survival rate was 38 percent among those separated in the neonatal period, as compared with 64 percent among those separated after the first month.
Early separation is indicated when one twin threatens the life of the other.
To assist in planning the separation, a three- dimensional computer model of the conjoined twins was constructed on the basis of prenatal MRI studies. The most important information provided by MRI was related to the detailed anatomical structure of the biliary tracts and the spatial relation of the shared anatomical structures. We are indebted to Drs. All rights reserved.