Conjoined twin or popularly referred as Siamese twins-are twin joined in utero. It is a rare phenomenon with unknown exact aetiology. It is classified on the basis of the site of union, with the suffix -pagus (meaning fastened or fixed). For example; i. Thoracopagus : The twins lie face to face and are joined at the sternum, diaphragm, upper abdomen wall and liver and have an exomphalos. ii. Craniopagus: The conjoined twins share the skull, meninges and the venous sinuses. The brains are usually separate.