Prenatal diagnosis of beta-thalassaemia and other haemoglobinopathies in India.
This paper reports prenatal diagnosis of 787 fetuses of beta-thalassaemia and other haemoglobinopathies in Indian high-risk communities. DNA based diagnosis was offered in the first, as well as the second trimester, in 489 pregnancies (with five twins) on fetal tissues such as chorionic villus (CV) and amniocytes using the amplification refractory mutation system (ARMS) and restriction fragment length polymorphism (RFLP) techniques. Two hundred and ninety-two women (with one twin), who either presented late in the second trimester or whose DNA diagnosis was not informative, were offered prenatal diagnosis using globin chain synthesis (GCS) on fetal blood cells. Maternal contamination of fetal DNA was ruled out by variable number tandem repeat (VNTR) analysis using sites in four different genes (Apo-B, D1S-80, Ig-JH and Ha-ras), while contamination of fetal blood was checked by a particle size distribution channelyzer. Using both techniques we were able to offer complete diagnosis in 99.8% cases. Out of 494 fetuses tested by DNA analysis, 135 were found to be normal, 201 were carriers, whereas 146 were affected. Out of 293 fetuses analysed by GCS, 215 were unaffected and 71 were affected. In this study, both fetuses were tested in twin pregnancies, of which three required selective termination of one fetus. Because of social, religious taboos and family influences, genetic counselling was found to be an important guideline for couples selecting options for prenatal diagnosis. Our experience suggests that because of late presentation by many couples to the diagnostic centres, in developing countries like India, both the techniques of DNA analysis and GCS should be made available at major referral centres for maximum benefit to couples.