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.