The Role of Factor V Leiden in Maternal Health and the Outcome of Pregnancy

There is growing evidence that women with thrombophilia are at increased risk of pregnancy related venous thromboembolism and of adverse pregnancy outcome including pregnancy loss, pre-eclampsia, intrauterine growth retardation and placental abruption. The factor V Leiden mutation is a heritable thrombophilia present in 5-8% of Caucasian populations. In its heterozygous form it is associated with a 4-to 8-fold increase in thrombotic risk. Homozygous inheritance, however, confers around an 80-fold increase in relative risk of thrombosis. The relationship between factor V Leiden and adverse pregnancy outcome has been studied in the recent literature, however the size of the estimated risks varies between individual studies due to heterogeneity of study design and small sample size in many cases. The management of women with factor V Leiden in pregnancy with low molecular weight heparin has been shown to be both safe and effective in preventing venous thromboembolism and improving pregnancy loss. Large scale, randomised controlled studies are required to confirm these findings. Selective screening for factor V Leiden based on prior venous thromboembolism has been shown to be marginally more cost-effective than universal screening in pregnancy and a recent consensus statement has recommended screening for thrombophilia based on a strong personal or family history of venous thromboembolism. There is now some evidence that placental problems may be associated with factor V Leiden in the fetus. There has also been an observed association between maternal factor V Leiden and fetal or neonatal stroke. These areas require further study and at present there is no evidence-based approach to investigation, prevention or management.