Haematological Aspects of Antenatal Diagnosis for Thalassaemia in Britain

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Abstract
The results are described of 200 antenatal diagnostic tests for hemoglobinopathies performed on samples of fetal blood obtained during the 2nd trimester of pregnancy. Hb A synthesis in the fetus was measured by incorporation of tritiated leucine in vitro and separation of the globin chains on CM23 columns. The range of HbA synthesis detected was 3.5-8.0% in normal fetuses, 2.0-5.0% in fetuses with thalassemia trait, and < 1.6% in fetuses with thalassemia major. There were 8 cases in which other hemoglobinopathies were diagnosed. Of the pregnancies studied, 29% were terminated because thalassemia major was diagnosed, and 9.5% of the remaining healthy fetuses were lost for obstetric reasons. Follow-up has been possible for 96% of the 124 surviving babies and 3 misdiagnoses have come to light; 1 false positive (0.5%) and 2 false negatives (1%). These figures represent a first effort at antenatal diagnosis for hemoglobinopathies and it is likely that they will improve with the passage of time.