The effects of folic acid supplements on coagulation status in pregnancy.

Thromboembolic disease remains the leading cause of maternal death in the UK. Recent literature has proposed that folate status is a strong predictor for venous thrombosis. Using thrombelastography (TEG((R))), we tested the hypothesis that folic acid supplementation is associated with a reduction in whole blood coagulability. Blood samples and questionnaire data were obtained at a mean gestation of 13.6 weeks (SD: 3.8, range: 6-38 weeks) from unselected consecutive women attending for their antenatal booking scan. Of 588 patients, 439 (74.7%) took folic acid. All TEG((R)) parameters were less hypercoagulable in women that had taken folic acid compared with those that had not: mean maximum amplitude (MA) 60.3 versus 62.1; mean difference 1.8; 95% confidence interval 0.8, 2.8; P = 0.0001; mean coagulation index (CI) 0.54 versus 0.85; mean difference 0.31; 95% confidence interval 0.11, 0.5; P = 0.002. There was no difference in the incidence of the homozygous MTHFR mutation in patients taking folic acid (5.53%) compared with those that were not (4.08%). This study suggests that benefit may be derived from longer-term treatment, although large multicentre studies are required to determine whether the relative hypocoagulability is associated with a reduction in risk of venous thrombosis.