Unexpected rapid rise of maternal serum anti-D levels during pregnancy

Two cases are described where hydrops faetalis developed as a result of very sudden and unexpected rises in serum anti-D levels. In both cases intravascular intrauterine transfusion was employed and a favourable outcome obtained. These cases show that continued vigilance is required even when anti-D levels are low. Weak antibody titres may be detected using enzyme-treated red cells, and failure to use this more sensitive technique meant that in one of the cases the initial weak antibody was not detected. There is currently a debate about the use of this more sensitive test in view of the increased work involved.