Experience of a molecular genetics service in prenatal diagnosis by DNA analysis

Prenatal diagnoses of the genetic disorders alpha, beta thalassemia, HbS, Hb Lepore, hemophilia and cystic fibrosis were sought in 88 cases. Six unsuccessful attempts at diagnosis resulted from DNA polymorphisms which were only 50% informative (four cases) and prenatal diagnoses which had been undertaken before it was known whether DNA polymorphisms in family studies were informative (two cases). The most frequent indications for prenatal diagnosis were the hemoglobinopathies although requests for exclusion of cystic fibrosis formed the majority during 1989. Strong linkage disequilibrium between the cystic fibrosis defect and its associated DNA polymorphisms facilitated detection of this disorder. Late presentations among patients with beta thalassemia and hemophilia and the necessity for more specialised genetic counselling were the commonest problems encountered.