Background: Subtelomeric deletion 1p is difficult to detect from banded karyotypes. Recent developments in the field of molecular cytogenetics have made it possible for submicroscopic rearrangements within chromosomes to be detected using fluorescence in situ hybridization (FISH) techniques.
Materials and methods: We describe prenatal FISH testing of subtelomeric 1p deletion in a fetus of a mother whose previous child had subtelomeric 1p deletion.
Results: Fluorescent in situ hybridization from fetal cells demonstrated normal 1p, thus predicting a very high likelihood of an unaffected fetus. The study was confirmed by the birth of a normal neonate.
Conclusions: We report the use of molecular genetic testing to exclude subtelomeric 1p deletion prenatally. Prenatal diagnostic testing for a known deletion is a reasonable option for couples at risk for having a child with subtelomeric 1p deletion. Molecular testing is more accurate and reliable than ultrasonography and provides families with reassurance.