Absence of Maternal Contamination of Chorionic Villi Used for Fetal-Gene Analysis

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Abstract
Chorionic villi can be obtained by direct transcervical aspiration at 9 to 10 weeks' gestation and used for analysis of fetal DNA. However, for the method to be reliable, there must be no detectable contamination by maternal DNA. To investigate the question of contamination, we compared the DNA of chorionic villi from five fetuses with that obtained from maternal lymphocytes, using the restriction endonuclease TaqI and specific DNA probes for a pair of alleles on the X chromosome. The alleles yield fragments of different lengths when digested with TaqI (length polymorphism), which can be demonstrated by electrophoresis and hybridization with the radioactive DNA probes. If the pattern obtained with the chorionic DNA is different from that obtained with the maternal DNA, contamination is not present.