Prenatally detected fetal myelomeningocele: is karyotype analysis warranted?

PURPOSE To determine the prevalence of karyotype abnormalities in fetuses with prenatally detected spina bifida and evaluate the ability of prenatal sonography to enable prediction of chromosomal abnormalities. MATERIALS AND METHODS Sonograms from 63 fetuses with prenatally detected spina bifida were reviewed, and associated sonographic abnormalities were recorded. Sonographic findings were correlated with autopsy or clinical findings when possible. RESULTS Associated sonographic abnormalities were present in 15 (24%) of fetuses with spina bifida. Among 52 fetuses with known karyotypes, the prevalence of chromosome abnormalities was 17%. Karyotype abnormalities included trisomy 18, trisomy 13, triploidy, and translocation. Twenty-two percent of chromosomally abnormal fetuses had sonographically isolated spina bifida. CONCLUSION Prenatal sonography can help predict most karyotypically abnormal fetuses with spina bifida, but approximately 20% will be missed with this technique alone in the second trimester. The authors believe cytogenetic analysis is justified in the setting of prenatally detected spina bifida.