Factor VIII-related antigen and factor VIII coagulant activity in normal and pre-eclamptic pregnancy.

The changes in the ratio between factor VIII-related antigen and factor VIII activity were compared in ten patients with normal pregnancies and in ten patients with severe pre-eclampsia. In the patients with pre-eclampsia, a highly significant increase in the ratio was observed during the third trimester. No difference in the ratio between the two groups was found on day 7 of the puerperium. In the pre-eclamptic patients, the highest ratios for factor VIII-related antigen to factor VIII activity were associated with either a perinatal death or with the delivery of a severely growth retarded infant. These findings are in keeping with an increased rate of thrombin production in women with pre-eclampsia, and suggest that the ratio of factor VIII-related antigen to factor VIII activity may reflect the severity of the effect of the disease process on the fetus.