Prenatal Diagnosis and Screening of the Haemoglobinopathies

The most important aspects of carrier detection procedures, genetic counselling, population screening and fetal diagnosis of the thalassaemias and sickle cell anaemia are reviewed. Carrier detection can be made retrospectively, i.e. following the birth of an affected child, or prospectively. Most carrier detection and genetic counselling in population at risk for alpha-thalassaemia an sickle cell anaemia is retrospective. However, some prospective carrier screening programmes for sickle cel anaemia are ongoing in Cuba and Guadeloupe and very limited screening for alpha-thalassaemia is in progress in some South East Asian populations. As regards beta-thalassaemia, several programmes, based on carrier screening and counselling of couples at marriage, preconception, or early pregnancy, have been operating with several populations at risk in the Mediterranean. These programmes have been very effective, as is proved by the fact that the target population has improved its knowledge of thalassaemia and its prevention, and by the marked decline that has been observed in the incidence of thalassaemia major. Carrier detection is carried out by haematological methods, followed by mutation detection by DNA analysis. Prenatal diagnosis is accomplished by mutation analysis on PCR-amplified DNA from chorionic villi. Future prospects include automation of the process of mutation detection, simplification of preconception and preimplantation diagnosis, and fetal diagnosis by analysis of fetal cells in the maternal circulation.