Why are thalassaemia patients born when prenatal screening is available?

Thalassaemia major is a classic example of a disease that is preventable by prenatal diagnosis. Although the technology was introduced to Hong Kong more than a decade ago, new patients are continuously seen in the Hong Kong Administrative Region. This retrospective review concerns children who were diagnosed to have severe beta-thalassaemic syndromes at the Tuen Mun Hospital from 1990 to 1996. Seventeen children (including a pair of identical twins) with homozygous beta-thalassaemia and five children with double heterozygous beta-E thalassaemia were identified. All except three children were transfusion-dependent. Thirty-six parents were available for the thalassaemic study. Thirty-one of them had beta-thalassaemic traits and the other five were carriers of haemoglobin E. Two of the parents with beta-thalassaemic traits and all five haemoglobin E carriers had a mean corpuscular volume above the cut-off for screening in antenatal diagnosis (>75 fL). Of the 21 at-risk pregnancies, seven were managed by public hospitals, 11 by maternal and child health centres, and two by private practitioners. Thalassaemia had not been diagnosed prenatally because of the lack of maternal screening (n=9), lack of paternal screening (n=3), late antenatal visit (n=7), and parental refusal (n=1). Thus, many of our patients are not benefiting from the availability of prenatal screening.