Karyotyping for isolated neural tube defects: A report of two cases

BACKGROUND: Neural tube defects occur in approximately 1 in every 1,000 live births. In the United States, chromosomal abnormalities have been noted in 2-10% of fetuses with neural tube defects; however, there is no consensus on whether to offer karyotype analysis to patients with isolated neural tube defects found on ultrasound. CASE: We reviewed the prenatal diagnosis database for the University of Washington between 1985 and 1997. We report on two fetuses who, on ultrasound, were found to have 'isolated' neural tube defects. Karyotype analysis revealed trisomy 18 in both fetuses. The pregnancies were subsequently terminated, and autopsy revealed subtle syndromic findings that were not identified on ultrasound. CONCLUSION: Fetuses with isolated neural tube defects also appear to have a high risk of chromosomal abnormalities, so patients should be offered fetal karyotyping to define recurrence risks for future pregnancies.