Objective: To compare two methods of obtaining fetal cells from the endocervical canal for prenatal diagnosis during the first trimester: lavage with physiologic saline, and the endocervical passage of a cytobrush.
Methods: Fetal cells were identified morphologically using conventional and immunohistochemical staining. Y-specific sequences were detected using polymerase chain reaction (PCR) and fluorescent in situ hybridization. The presence of fetal DNA was also demonstrated by PCR amplification of a polymorphic short tandem repeat marker.
Results: Syncytiotrophoblast cells were identified in four of 11 lavage samples and in one of 11 brush samples. Sex determination using fluorescent in situ hybridization was achieved in all 11 lavage samples and in nine of 11 cytobrush samples; no Y sequences were located in two brush samples from male embryos. Sex determination was achieved successfully in all 22 samples using PCR of X- and Y-specific DNA sequences. Small tandem repeat pattern analysis indicated the presence of fetal DNA in five of 11 lavage samples and in one of eight cytobrush samples, which were informative because the maternal and fetal small tandem repeat patterns differed.
Conclusion: Although lavage retrieves more trophoblast cells than does brushing, both methods are potentially suitable for molecular prenatal diagnosis.