acardius
noun
acar·dius
| \ (ˈ)ā-ˈkärd-ē-əs
\
\
Medical Definition of acardius
: one of a pair of twin fetuses that develops without a heart and receives its blood supply from its twin through vascular connections on the placenta
… due to the parasitic relationship of the acardius, there is a high risk of mortality (50-75%) in the donor twin …— Ona Marie Faye-Peterson et al., Handbook of Placental Pathology, 2006