Conjoined twins

Conjoined twins (CT) are an extremely rare group of identical twins. Their incidence shows a highly variable value. They are expected, on average, one in every 50,000–100,000 pregnancies, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and an additional one-third dies within 24 h. Most live births are females, with a ratio of 3:1. In total, 70% are fused at the thorax or abdomen. Congenital anomalies unrelated to the site of union have been reported in 40%–60% of CT. Their overall survival rate ranges from 5% to 25%, with about 75% of surgical separations resulting in at least one twin surviving. The etiology of their formation is as unknown as that of identical twins. There have been no genetic, environmental, or demographic factors found to be associated with the etiology of CT. Management and surgical separation of CT still remain a challenge to modern sciences due to multiple congenital anomalies.