Quantitative Fluorescent PCR (QF-PCR) is a simpler and faster method of detecting common chromosomal abnormalities when compared to cytogenetic analysis. The aim of our study is to investigate the applicability of this methodology in a population where consanguineous marriages are common and to estimate the heterozygous frequency of the PCR markers used.Four hundred and twenty-three DNA samples were extracted from uncultured amniocytes and amplified with 18 short tandem repeats (STR) markers specific to chromosomes 13, 18 and 21. Amplification products were analyzed using the GeneScan software.QF-PCR correctly identified all the numerical abnormalities related to chromosomes 13, 18 and 21. A total of 24 autosomal trisomies (5.7%) were detected. The markers D21S1432 and D21S11 were the most consistent in providing unequivocal positive results for chromosome 21 and the heterozygosity percentages of the markers used were lower than the values reported in Western populations.QF-PCR is reliable for the prenatal diagnosis of numerical anomalies of the chromosomes 13, 18 and 21 in our study population. The absence of STR heterozygosity data from Lebanon and surrounding countries makes our study very useful for the development of a reliable QF-PCR trisomy detection test.