Prenatal sonographic diagnosis, Doppler velocimetric umbilical cord studies, and subsequent management of an acardiac twin pregnancy.

Sonographic prenatal diagnosis and management of a twin pregnancy complicated by acardius anceps of one twin and acute polyhydramnios is presented. To our knowledge, this is the first case of an acardiac twin gestation in which Doppler umbilical arterial velocimetric studies were obtained. These studies, performed at 29 weeks' gestation, demonstrated markedly different umbilical artery systolic to end-diastolic (S/D) ratios in the twins. This difference is explained by the vascular resistance reflected in the umbilical artery S/D ratios obtained on each twin. The healthy twin's S/D ratio represented the vascular resistance of the placenta and the perfused acardiac twin. Because of the reversed direction of blood flow in the acardiac twin's umbilical artery, this S/D ratio represented the vascular resistance of the acardiac twin. Planned preterm delivery resulted in survival of the healthy normal twin.