Diagnosing chromosomal abnormalities from "big" to "small" with molecular cytogenetic technology.

We reviewed the available molecular cytogenetic techniques and their potential use in prenatal diagnosis of fetuses with multiple congenital anomalies and a "normal" standard chromosomal karyotype. We searched Medline to identify reports published after 1995 that were related to molecular prenatal diagnosis. After review, we reached the following conclusions: 1. In fetuses with a normal standard karyotype result, common chromosomal microdeletion syndromes may be suspected based on the pattern of congenital anomalies seen on prenatal ultrasound. 2. When a microdeletion syndrome is suspected based on the pattern of fetal anomalies, FISH testing for the specific molecular locus should be undertaken. 3. Routine chromosome analysis, which has been the gold standard for prenatal cytogenetic diagnosis, may in the future be replaced by microarray technology with increased diagnostic capability for smaller, submicroscopic genetic alterations associated with postnatal morbidity. 4. Microarray technology has been shown to increase our ability to make a diagnosis of known or new chromosomal deletion syndromes in pediatric populations with developmental delay. The use of this technology for prenatal diagnosis is currently limited but is likely to expand.