YK Ng, P Ip, BCC Lam

Severe fetal anaemia is defined as a haemoglobin level less than 10 g/dl. From 1991 to 1996, six cases of prenatally diagnosed severe fetal anaemia (excluding α-thalassaemia major) were referred to Tsan Yuk Hospital for further management. The mean haemoglobin level was 4.75 g/dl (range 2.8-7.2). All of them showed hydropic changes before delivery. The aetiology includes Rhesus isoimmunization (2), haemolytic disease due to anti-M antibody (1), haemolysis of unknown cause (2) and microangiopathic haemolytic anaemia related to placental haemangioma (1). Two fetuses with Rhesus isoimmunization were treated by intra-uterine intravascular fetal transfusion. All babies were delivered prematurely (mean gestation age 31.8 weeks, range 29-35 weeks). Five babies required packed cell exchange transfusion for correction of severe neonatal anaemia. All babies with haemolytic causes suffered from a protracted course of postnatal anaemia with low reticulocyte reaction, more severe in those treated with intra-uterine transfusion. All babies showed normal neurological development on long-term follow up. In summary, Rhesus isoimmune haemolytic anaemia is rare in Southern Chinese. Early prenatal diagnosis and intervention significantly improve the outcome. Packed cell exchange transfusion proved to be effective in the treatment of severe neonatal anaemia. The correction of anaemia may suppress the production of erythropoietin with impairment of marrow response, and the newly produced reticulocytes may be destroyed by the existing antibodies, contributing to the protracted post-natal anaemia.