Antenatal Diagnosis of the Haemoglobinopathies

The β‐chain of adult haemoglobin is expressed in fetal red cells during the first to mid‐trimester of human pregnancy. The rate of β‐chain production is approximately 8% of γ‐chain production during this period of gestation. The production of β^s‐chains is readily detectable and the reduction of β^A‐chain production in thalassaemia may also be observed. Acquisition of fetal cells by means of placentocentesis or placental venipuncture via a fetoscope are current sampling methods which have been shown to be useful. Thus far five attempts at such antenatal diagnosis have been made, four for β‐thalassaemia and one for sickle cell anaemia. In three of these attempts (all for β‐thalassaemia), a sample of fetal blood was obtained. In one, the correct diagnosis of a normal fetus was made. In a second fetus, the diagnosis of β‐thalassaemia trait was made; the infant was normal. In a third, the diagnosis of a normal fetus was made; the infant had β‐thalassaemia trait. These early results indicate that attempts at antenatal diagnosis of the common β‐chain abnormalities do not necessarily disturb pregnancy and can yield important information which encourages mothers at risk to retain pregnancies.