Prenatal diagnosis of cystic fibrosis: a case of twin pregnancy diagnosis and a review of 5 years' experience

We performed prenatal diagnoses for cystic fibrosis in 32 high risk (1:4) c ouples (including a dizygotic pregnancy). Chorionic villi sampling did not cause abortion or fetal malformation in any case, The preliminary analysis of 9 short tandem repeats always excluded maternal contamination of the DNA extracted from chorionic villi and confirmed paternity. Twenty-two prenata l diagnoses were made by direct analysis of the mutations, In seven cases d iagnosis was made by the analysis of intragenic polymorphisms; in three cas es, we analyzed two extragenic polymorphisms. The prenatal diagnosis (inclu ding genetic counselling) was completed within 24 h from the sampling. Seve n prenatal diagnoses revealed an affected fetus; all couples opted for ther apeutic abortion. In 17 cases the fetus was heterozygote, and in seven case s it was non carrier of mutated alleles. In the twin pregnancy, mutations w ere Delta F508/N1303K. Direct analysis of the DNA extracted from the two in dependent samples of chorionic villi revealed one fetus non carrier of muta ted alleles and the other a carrier of the N1303K mutation. Analysis of the HPRT locus predicted both the fetuses as males. Furthermore, the genotype of each fetus was defined after birth. The prenatal diagnosis with chorioni c villi sampling plays a key role in the prevention of cystic fibrosis. The laboratories must he equipped for both the direct analysis of mutations an d for the analysis of a large number of polymorphisms. The preliminary anal ysis of short tandem repeats is recommended both to exclude maternal contam ination and to confirm parentage. (C) 2000 Elsevier Science B.V. All rights reserved.