Thoracopagus twins; prenatal diagnosis.

While the delivery of conjoined twins is one of the rarities of obstetrical practice, the increasing frequency of routine prenatal roentgen studies makes it imperative that the radiologist recognize this anomaly so that he may forewarn the referring obstetrician of the problem to be faced. In as careful a review of the literature as was possible, though admittedly incomplete, only one case (1) was found in which a roentgen diagnosis of conjoined twins was made before delivery; two additional examples (2, 3) have been discovered through personal correspondence. The following case is presented to call attention to several points which may aid in the prenatal roentgen recognition of this developmental anomaly. While the modus operandi in the production of Siamese twins is not conclusively known, a number of theories (4, 5) have been advanced, one or the other of which may be the explanation in any given instance. The best known theory, that of the separation of the two blastomeres formed by the first divisio...