Antenatal diagnosis of thalassemia: a review

The overall results of the WHO International Registry for the Prenatal Monitoring of Hereditary Anemias are summarized in Tables 11 and 12. Comparison of data regarding adequacy of samples, and freedom from errors and from fetal losses show that the chance of a couple obtaining a useful result is greater than 90%, whether fetal flood is sampled because the fetus is at risk for a hemoglobinopathy or another disease, or fetal DNA is obtained for globin gene analysis. Each approach serves as a model for the others. Fetal blood sampling technology has been improved because of the need for entirely pure samples for diseases requiring specimens other than red cells. The advances in obtaining fetal cells early in pregnancy and extraction of DNA will soon be applied to diseases other than hemoglobinopathies (such as hemophilias and muscular dystrophies) as molecular probes become available. More than 6000 fetuses have now been examined in utero, 5617 for all hemoglobinopathies using fetal blood or DNA, and 5921 for all disorders using fetal blood (Table 12). The total reported to the Registry by the end of 1983 was 6282 cases. At the moment, the only choices when an affected fetus is detected are termination of the pregnancy, or delivery of a child known to have a serious and sometimes life-threatening illness. However, early diagnosis will lead to early treatment of such infants, thereby offering a better prognosis. When specific treatment such as gene therapy becomes available, fetal diagnosis will identify the appropriate cases in utero. Although this approach is currently speculative, it is an area of great interest and endeavor. Thus, prenatal diagnosis of hemoglobinopathies has led to the development of fetal diagnosis of many genetic diseases, and resulted in techniques for obtaining fetal blood or DNA specimens. In addition to these scientific advances, it has also led to the control of thalassemia in certain geographic areas in which the public health burden involved in the management of such cases is overwhelming. Reduction of the number of newborn thalassemics is a necessity in some places, because appropriate care has not been possible, and the lifespan of affected individuals is significantly shortened or at least uncertain. All approaches to management of this disease are relevant, including improved treatment, specific therapy, and prenatal diagnosis. Each country and each family must determine for itself where to place the emphasis.