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.