False negative cytogenetic results following amniocentesis.

We report 2 cases where prenatal cytogenetic studies following amniocentesis yielded false negative results. Both mothers requested termination of pregnancy but were reassured by the normal chromosome analysis and therefore continued their pregnancies. When cytogenetic studies were repeated in the neonatal period, they demonstrated chromosomal abnormalities, which were confirmed when the initial specimens from amniocentesis were reviewed. Because of our findings, we suggest that if prenatal chromosome analysis is reported as normal, where there is a high index of suspicion of a chromosome abnormality, the result should be questioned and neonatal chromosome analysis undertaken.