Editor—The presence of trophoblastic cells in the endocervical canal of pregnant women between 5-7 and 13-15 weeks of gestation has been repeatedly confirmed.1 2 Using fluorescence in situ hybridisation (FISH) or the polymerase chain reaction (PCR) assay, chromosome Y derived sequences have been detected in trancervical cells (TCCs) retrieved from mothers with male fetuses.

Although small tandem repeats (STRs) and quantitative fluorescent PCR (QF-PCR) have also been used to monitor the presence in TCC samples of fetal DNA sequences inherited from the father and absent in the mothers,1 3 the direct and unequivocal demonstration of trophoblastic cells derived from female fetuses has been hampered by the unavailability of highly polymorphic markers specific for the X and Y chromosomes.

In this pilot study, we have assessed the diagnostic value of using a new X/Y chromosome marker, X22,4 for the detection of trophoblastic cellular elements released into the endocervical canal by female fetuses.

After receiving verbal consent, samples were retrieved by cervical mucus aspiration1 from four pregnant women, at about 10 weeks of gestation, before termination of pregnancy. Maternal peripheral blood and …