Investigation of acephalus.

We report twins, one of whom was diagnosed as grossly abnormal by ultrasound at 28 weeks' gestation. Postmortem angiographic investigation of this acardiac twin and of the inter-fetal placental anastomoses are reported. The acardiac fetus had a 45,X chromosome constitution, while the other twin had apparently normal chromosomes (46,XX). The association of chromosome anomaly with holoacardius acephalus is discussed.