[Molecular biology usefulness for rapid diagnosis of Down's syndrome and common aneuploidies]

Trisomy of chromosome 13, 18, 21 and sex chromosome aneuploidies are the most common chromosomal abnormalities encountered in prenatal screening and are responsible for polymaformative syndrome associated with severe mental retardation. This high degree of morbidity justifies the prenatal diagnosis of these aneuploidies. Fetal nuchal translucency measurement and maternal serum biochemical marker assessment are the method of choice used for antenatal screening of aneuploidies. This prenatal screening leads to numerous maternal samplings followed by karyotyping which is cost-effective, time consuming, while results are generally returned between 2 and 3 weeks. Our study describes the research of common aneuploidies by molecular biology. We have used on one hand the MLPA kit (MRC Holland) based on amplification of specific DNA probes that hybridize with chromosomes 13, 18, 21, X, Y. On the other hand we have developed multiplex fluorescent PCR, amplifying microsatellite DNA sequences.

We have evaluated the efficiency of these two techniques to detect chromosomal abnormalities by screening 400 amniotic fluids or chorionic villi samples obtained from pregnant women presenting a high risk of chromosomal aneuploidy.

We have found four trisomies 21, one trisomy 13, one monosomy 13, one trisomy 18, two triploidies, one trisomy X and one Klinefelter syndrome.

In our study we have detected by molecular biology, in less than 48 h, 100% of common chromosomal aneuploidies without false positive or false negative results which could lead molecular biology as a method of choice for the rapid detection of common aneuploidies in addition to fetal karyotyping.