Prenatal diagnosis of inherited hemoglobinopathies.

In this paper we reviewed the different methods presently available for prenatal diagnosis of hemoglobin disorders and the impact of this technology in the control of beta-thalassemia in several Mediterranean populations. The vast majority of the inherited hemoglobinopathies can now be detected in the fetus by amniocyte or trophoblast DNA analysis. alpha-thalassemias, delta beta-thalassemias and gamma delta beta-thalassemias, which are usually caused by a gross structural rearrangement of the DNA, may be directly detected by Southern blot analysis. Only a few beta-thalassemia lesions are caused by gene deletion or affect a restriction recognition site and thus may be directly identified by this method. The major part of beta-thalassemia are due to single nucleotide substitution, small deletion or addition which do not alter a restriction recognition site. These mutations may be directly detected by complementary oligonucleotide probes. Alternatively, when normal or affected children are available, fetal diagnosis may be accomplished by linkage analysis with polymorphic restriction sites. Fetal blood analysis is used at present time for those cases presenting too late in the pregnancy for characterization of the molecular defect and in prospective parents in whom the defect is not known. Introduction of prenatal diagnosis in combination with carrier screening in several mediterranean populations led to a consistent reduction in the incidence of homozygous beta-thalassemia.