Fetal nuchal translucency and prenatal diagnosis of β‐thalassaemia

In Sardinia, fetal karyotyping for couples at risk for β‐thalassaemia is offered only to women ⩾35 years and for specific risk of chromosomopathies. This policy is not easily accepted by the couples who insistently request additional karyotyping. In order to select those at highest risk of chromosomal abnormalities among young women, fetal nuchal translucency (NT) thickness measurement was performed in 510 fetuses to assess the chromosomal risk before chorionic villus sampling. A risk ⩾1/100 was judged positive and worthy of additional karyotyping. 126 cases interrupted the pregnancy after a result of homozygous β‐thalassaemia, hence 384 pregnancies were included in the study. 22 (5.7 per cent) fetuses were found NT positive. A total of three chromosomal abnormalities were detected. The NT test was positive in all three cases of chromosomopathies detected (100 per cent) and in 19 of 381 (4.98 per cent) normal karyotype fetuses. No features of major chromosomal abnormalities were reported among the newborns whose NT had resulted normal. These preliminary results have confirmed the efficacy of NT testing to assess the risk of trisomy 21 and other chromosomopathies and enhanced its utility in pregnancies already suited to sampling in the first‐trimester for Mendelian disorders. Copyright © 1999 John Wiley & Sons, Ltd.