Acardia: predictive risk factors for the co-twin's survival.

This study aimed to find factors in acardiac pregnancies that could be used to predict survival rates of the pump fetus. Five cases of acardia at Monash Medical Centre were found, and all case reports available in the literature from 1960 to 1991 (184 cases) were collected and analyzed. Acardia is more common in nulliparous women and in monoamniotic monochorionic pregnancy. The acardiac fetus usually has a two-vessel umbilical cord and is most likely to develop structures supplied by the lower aortic branches. Delivery is more often preterm (mean gestation = 31.1 weeks) than normal twins. The overall perinatal mortality for the pump fetus is 35% in twins and 45% in triplets. Factors associated with a statistically significant increase in perinatal mortality for the pump fetus include delivery before 32 weeks gestation, acardiacus anceps form of acardia, and the presence of arms, ears, larynx, trachea, pancreas, kidney, or small intestine in the acardiac fetus. Active intervention in these pregnancies is reasonable.