First trimester diagnosis of β-thalassaemia in a twin pregnancy

This paper reports the results of first trimester prenatal diagnosis in a twin pregnancy at risk for homozygous β°?thalassaemia (β°?39 mutant). Trophoblast samples from both twins were obtained at 10 weeks gestation with a forceps guided by ultrasound. Trophoblast DNA analysis, carried out with the oligonucleotide technique, revealed that one fetus was homozygous and the other heterozygous for the β?39 mutant. This diagnosis was confirmed at 17 weeks gestation by amniocyte DNA analysis. DNA polymorphism analysis within the α-globin gene provided useful genetic markers for twin differentiation.