Arg506-Gln mutation in factor V and risk of thrombosis during pregnancy.

Seventy women with thrombosis in pregnancy were investigated for the presence of APC resistance and the associated Arg506-Gln mutation in coagulation factor V. The mutation was found in 46% of the investigated women. Carriers of the mutation were more prone to develop thrombosis in the first pregnancy (OR (odds ratio) = 3.41; P < 0.05) and had a higher probability of recurrence (OR = 3.86; P < 0.05) compared to non-carriers. The incidence of miscarriage was not related to the mutation but its probability increased in women with thrombosis in a second or subsequent pregnancy (P < 0.025). Negative dynamics of APC response during pregnancy was observed in 20/22 women; eight of them developed APC resistance de novo. The suppression of APC response was independent of the mutation.