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

List of authors.
  • Robert G. Elles, B.Sc., M.SC.,
  • Robert Williamson, Ph.D.,
  • Meena Niazi, Ph.D.,
  • Dulcie V. Coleman, M.D.,
  • and David Horwell, M.R.C.O.G.

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.

In two cases the fetal DNA of the chorionic villi was shown to be uncontaminated by maternal tissue. In one of these cases the mother was heterozygous and the fetus was homozygous; in the other the mother was homozygous and the fetus was heterozygous. In three other cases no definitive conclusions could be drawn, because the genotypes of the fetus and mother were identical. We conclude that chorionic villi at 9 to 10 weeks' gestation are a source of fetal DNA that can be used for gene analysis, with no detectable contamination by maternal DNA. (N Engl J Med 1983; 308:1433–5.)

Funding and Disclosures

Supported by grants from the Medical Research Council, the Cystic Fibrosis Research Trust, and Birthright.

We are indebted to Dr. Peter Pearson, University of Leiden, for probe L1.28, and to Drs. Kay Davies and Frank Loeffler for many helpful discussions.

Author Affiliations

From the Departments of Biochemistry, Cytology, and Obstetrics, St. Mary's Hospital Medical School, University of London, Address reprint requests to Mr. Elles at the Department of Biochemistry, St. Mary's Hospital Medical School, London W2 1PG, England.

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