Prenatal diagnosis of trisomy 21 through detection of trophoblasts in cervical smears

Background: Fetal cells exfoliate in the uterine cavity during early pregnancy and are a potential source of material for NIPD. Aims: This study was designed to test the hypothesis that fetal cells obtained from the uterine cervix during the first trimester of pregnancy could be utilized for prenatal diagnosis of chromosomal aneuploidy. Study design: Fetal cells retrieved from the distal endocervical canal during the first trimester of pregnancy were hybridized with chromosome 21 specific FISH probes and analyzed with an automated fluorescence microscope. Subjects and outcome measures: Cells with 3 copies of chromosome 21 were detected in 5 out of 5 trisomy 21 pregnancies. Results: The number of trisomic cells detected ranged from 1 to 27 with a median value of 5. Conclusions: FISH-based scanning can identify trisomy 21 pregnancies by analysis of routine cervical brushings. The approach offers the potential for non-invasive prenatal diagnosis as early as 5. weeks gestation.