DETECTION OF FETAL CELLS IN TRANSCERVICAL SAMPLES AND PRENATAL-DIAGNOSIS OF CHROMOSOMAL-ABNORMALITIES

Transcervical samples collected by lavage, aspiration, and cytobrush f rom women between 6 and 13 weeks of gestation were tested for the pres ence of fetal cells using fluorescence in situ hybridization (FISH) wi th probes for chromosomes X, Y, 1, and 21, and by polymerase chain rea ction (PCR) amplification of DNA sequences derived from chromosomes X, Y, and 21. With a few exceptions, a good correlation was observed bet ween the results of sexing the fetuses using FISH or PCR on transcervi cal cell (TCC) samples retrieved by lavage and those obtained by testi ng fetal (placental) tissue. In a comparative study between TCC sample s collected by lavage or cytobrush, the sex of the fetus was correctly diagnosed by PCR amplification of a Y-derived DNA sequence. Variable results were observed with samples obtained by aspiration, mainly beca use this procedure was found to be more prone to failure to remove thi ck mucus without previous injection of physiological saline. Chromosom e 21-derived small tandem repeats (STRs) of fetal origin were successf ully detected in about 40 per cent of TCC samples recovered by lavage. Two cases of chromosomal abnormalities, one of trisomy 21 and one of triploidy, were detected in TCC samples in the course of our investiga tions.