Value of maternal anti-D concentration in predicting the outcome of Rh(D) haemolytic disease.

The outcomes of 43 pregnancies complicated by the presence of Rhesus antibodies were studied in relation to the peak concentrations of anti-D reached during pregnancy. Antibody concentration was measured by an automated method calibrated against the British Anti-D Working Standard. Where the anti-D concentration remained below 5 IU/ml, the infants at worst suffered only moderate jaundice controllable with phototherapy. Above this level the incidence of requirement for exchange or top-up transfusion was high with concentrations greater than 50 IU/ml being predictive of a very severely affected fetus. It is recommended that amniocentesis in these patients be deferred until maternal anti-D levels exceed 5 IU/ml.