Prevalence of aneuploidy and additional anatomic abnormalities in fetuses with open spina bifida: population based study in Utah.

Data were used to determine the population prevalence of aneuploidy and additional anatomic abnormalities in fetuses with open spina bifida. The ability of sonography to predict aneuploidy and identify additional anatomic abnormalities in euploid fetuses was assessed. All cases of spina bifida occurring in the state of Utah from 1995 through 1997 were reviewed using Utah Birth Defect Network data, including stillborn, liveborn, and terminated cases. Chromosomes were known in 45 of 51 cases of open spina bifida. Of the 45 fetuses, 6 (13%) were aneuploid. Major anatomic abnormalities were present in four of six (67%) cases, and two of six (33%) cases had additional anomalies that could be missed sonographically. Of 39 euploid fetuses, 12 (31%) had additional abnormalities, but only half likely would be detected sonographically. Our 4% risk of aneuploidy in sonographically isolated spina bifida is substantially higher than the risk associated with advanced maternal age (0.37%).