Molecular diagnosis of sex chromosome mosaics in fetal amniotic cells

Mosaicism can be observed in karyotype analyses of amniotic fluid cells. Differentiating between true mosaicism and pseudomosaicism and determining mosaic proportions can help avoid misjudgments by doctors and effectively reduce mental and physical harm to pregnant women. However, the detection of mosaicism and mosaic proportions via karyotype analysis and fluorescence in situ hybridization (FISH) is extremely complex. We have developed a novel approach, “segmental duplication quantitative fluorescent PCR” (SD-QF-PCR), to detect mosaicism and mosaic proportions. In this study, twenty control samples and fourteen mosaic samples were tested by first-line karyotype analysis; by second-line karyotype analysis, SD-QF-PCR and FISH were used to reassess fetal sex chromosome mosaicism and mosaic proportions. Detection of the 20 control samples by second-line karyotype analysis via FISH and SD-QF-PCR showed normal and consistent results. Among the 14 mosaic samples, the numbers of samples showing true mosaicism and pseudomosaicism detected by the three methods were 6 and 8, respectively. Our study demonstrates that SD-QF-PCR can be used as a complementary method to traditional cytogenetic analysis of amniotic fluid mosaics and has clinical application value.