Chorionic villus sampling for first trimester diagnosis of beta-thalassaemia. Report of the first South African case.

The first South African report of chorionic villus sampling for molecular diagnosis of beta-thalassaemia in a 10-weeks' pregnant Indian Muslim woman is presented. The sampling procedure and molecular techniques for sexing the fetus and establishing whether it was affected by beta-thalassaemia are described. From the sample of villi obtained a male fetus was identified, using an X-Y-specific DNA probe. A preliminary family study on both parents, the affected proband and his 4 phenotypically normal siblings, revealed two informative restriction fragment length polymorphisms in the mother, but none in the father. It was therefore not possible to differentiate between the two beta-globin gene alleles of the father. The fetus thus had a 50% chance of being a heterozygote or a 50% risk of being affected. Synthetic oligonucleotide hybridization of parental and fetal DNA was attempted by the Genetics Unit of Johns Hopkins Hospital, Baltimore, but the fetal hybridization was unsuccessful. Results on the parents were obtained too late to be of assistance in the present pregnancy as the parents requested termination of the pregnancy before 16 weeks' gestation for religious reasons.