types of conjoined twins

Conjoined twins are usually classified by the point at which they are joined (the Greek word pagos, meaning “that which is fixed.”) Here are some of the main types:

craniopagus

head-to-head, about 2% of all conjoined twins

pyopagus

pelvis-to-pelvis, about 19% of all conjoined twins

parapagus (sometimes called diprosopus)

lateral union of the trunk, about 5% of all conjoined twins. Heart sometimes involved

cephalothoracopagus

fusion of head and thorax

thoracopagus

chest-to-chest, the most common form of conjoined twins (about 35%). The heart is usually shared and there are associated vascular abnormalities, complicating surgical separation

(adapted from: Carlson, B.M. (2019) Human embryology and developmental biology. St. Louis: Mosby-Year Book, Inc., p 43.)