First-trimester prenatal diagnosis of a familial subtelomeric translocation

A new fluorescent in situ hybridization (FISH) technique utilizes a complet e set of telomeric probes to screen for deletions or rearrangements within the subtelomeric regions of all chromosomes on a single slide. Such cryptic chromosome rearrangements would otherwise remain undetected by standard cy togenetic analysis. In this case report, we describe the first-trimester prenatal diagnosis of an unbalanced rearrangement in a family where such a cryptic subtelomeric r earrangement is segregating. Interestingly the fetus Evils also noted to ha ve an increased nuchal translucency at the time first-trimester chorionic v illus sampling was performed and a FISH diagnosis made. The result was subs equently confirmed on fetal material obtained after elective termination of the pregnancy. We believe this to be the first report in the literature (as by Medline, De cember 1999) of a first-trimester prenatal diagnosis using such subtelomeri c probes where confirmation by conventional cytogenetic analysis was not po ssible.