#heartless fetus
- Acardia — A congenital absence of the heart or a complete cessation in the ontogenetic development of the cardiac structure in a fetus. This severe structural anomaly is incompatible with independent extrauterine life and is documented almost exclusively within monochorionic multiple pregnancies with asymmetric development (TRAP sequence), where the affected fetus's blood circulation is maintained solely by its twin's heart through placental vascular anastomoses.