Amniotic fluid anti-D and the maternal serum: liquor ratio in rhesus haemolytic disease of the newborn.

Eighty-seven pairs of samples of maternal serum and amniotic fluid were analysed for anti-D levels at varying stages of gestation. There was a marked positive correlation between the maternal serum level and that in the amniotic fluid. The ratio of maternal serum anti-D to liquor anti-D was calculated for 61 pairs of data and was found to increase as gestation advanced. However, it was neither of clinical value in predicting the severity of haemolytic disease of the newborn nor the Rh(D) group of the fetus.