Safely Ruling out Deep Vein Thrombosis in Pregnancy with the LEFt Clinical Decision Rule and and D-dimer (the LEaD study): A Prospective Cohort Study

Deep vein thrombosis (blood clots in leg veins) are a leading cause of sudden death in pregnant women in Canada. The symptoms of deep vein thrombosis, namely leg pain and/or leg swelling are very common in pregnancy leading to suspected deep vein thrombosis being a common occurrence in maternal health care settings. We have developed a simple, bedside, inexpensive, widely available approach consisting of a risk score (a clinical decision rule) and a blood test (D-Dimer) to exclude deep vein thrombosis in pregnancy. This would eliminate the need to do expensive, poorly available ultrasounds to exclude deep vein thrombosis in pregnancy. We will apply the LeFT clinical decision rule and do a D-Dimer blood test in 366 women with suspected DVT in pregnancy. In women with a low score (i.e. risk) with the rule and a negative D-Dimer blood test we will not do an ultrasound and follow them for 3 months for complications. Neither the LeFT clinical decision rule nor D-Dimer in pregnant women has been adequately validated to adopt into clinical practice. After completing this study, it is highly likely that these diagnostic tools will become standard of care in a simple, non-invasive, cost effective, widely available and safe diagnostic management strategy for the common problem of suspected DVT in pregnancy. This would represent a significant advance in maternal health.