Prenatal determination of fetal RhD type by DNA amplification from transcervical swabs

Objective We sought to utilize exfoliating trophoblasts that are shed into the endocervix as a source of fetal DNA for the purpose of molecular geneti c analysis. Methods Sixteen RhD-negative pregnant women were enrolled in this study. Ce rvical secretions collected with a cotton swab were fractionated to separat e out spermatozoa contamination from epithelial cells. The polymerase chain reaction (PCR) method was used on the epithelial cell fractions to analyze the fetal DNA for RhD gene and Y chromosome-specific sequences. These resu lts were correlated with the blood group and sex of neonates after delivery . Results The technique identified nine of 15 Rh-positive fetuses. Also, five out of six male neonates were identified by Y chromosome sequence amplific ation. Conclusion Specific fetal DNA sequences can be identified through simple ce rvical sampling of desquamated fetal trophoblasts combined with PCR amplifi cation. However, the accuracy of the test is low, making its clinical use i nconclusive in its present form.