Grant: Project Grant - Priority Announcement: Patient-Oriented Research

Individuals are at an increased risk of developing blood clots in the legs (deep vein thrombosis) and lungs (pulmonary embolism) during pregnancy and in the postpartum period after they give birth. Postpartum individuals who have additional blood clotting risk factors are often prescribed a daily injectable blood thinner (low-molecular-weight heparin). Previous studies have tested whether daily injectable blood thinners after delivery prevents blood clots, but one major barrier to study recruitment has been patients' lack of comfort with doing the injections at home. The injections are expensive. Aspirin has been shown to be effective at preventing blood clots after hip and knee surgery and is safe with breastfeeding. Our research team conducted a pilot trial (a test run) in postpartum individuals, and aspirin was an acceptable intervention. We will now conduct a large trial to answer the question if aspirin is non-inferior to the usual care injectable blood thinners, to prevent blood clots in their legs and lungs. After delivery, participants will be randomized to low-dose aspirin daily for 6 weeks or their usual care of injectable blood thinners. No extra blood tests or imaging tests are needed. There will be an online questionnaire at 6 weeks and 90 days. A telephone or in-person visit will only be needed if there were concerns raised from the online questionnaire, participant preference, or they did not answer the online questionnaire. The primary outcome is symptomatic blood clots up to 6 weeks after randomization. Other outcomes measured will include other blood clotting complications, bleeding complications, and death. If aspirin can safely prevent serious blood clots in the legs and the lungs after delivery and is similar to an injectable blood thinner, then re-purposing this simple, available and low-cost medication will answer an important knowledge gap and change practice in Canada and around the world.