Author(s): LEOPOLD ?LIWA, BARBARA MACURA
Etiology of the Siamese (conjoined) twins formation is currently unclear. An article discussesthe universally well-known, although contradictory, theories of Siamese twins development.This phenomenon is demonstrated in the context of normal process of embryo developmentduring critical period for this malformation (the third week of development). Probable factorsresponsible for the conjoined twins formation are discussed. What is more, the other types ofabnormal connections between fetuses are described, e.g. parasitic twins, fetuses in fetu oracardiacs. In addition, main medical and ethical problems, as well as the gaps in embryolo-gical knowledge connected with conjoined twins are briefly described.