i(18q) in amniotic and fetal cells with a normal karyotype in direct chorionic villus sampling: cytogenetics and pathology.

A case of false-negative discrepancy between results of chorionic villi (direct preparation) and those of fetal tissue with an isochromosome 18q [i(18q)] in amniotic cells and fetal blood is reported. Fluorescence in situ hybridization (FISH) confirmed this uncommon chromosomal rearrangement. The fetus showed cyclopia and multiple congenital anomalies which have never been reported in cases of i(18q).