A Parasitic twin is also known as an asymmetrical or unequal conjoined twin. Parasitic twins occur when a twin embryo begins developing in utero, but the pair does not fully separate, and one embryo maintains dominant development at the expense of the other. The undeveloped twin is defined as parasitic and the independent twin is called the autosite. The estimated incidence of heteropagus parasitic twins is approximately 1 per 1 million live births. Isolated case reports comprise most of published work on this rare congenital anomaly.
: V. Sudha Spandana