['The optimal timing of initiating low-molecular weight heparin (LMWH) in patients who have undergone nonoperative management (NOM) of blunt solid organ injuries (SOIs) remains controversial. We describe the safety of early initiation of chemical venous thromboembolism (VTE) prophylaxis among patients undergoing NOM of blunt SOIs.', 'We retrospectively studied severely injured adults who sustained blunt SOI without significant intracranial hemorrhage and underwent an initial NOM at a Canadian lead trauma hospital between 2010 and 2014. Safety was assessed based on failure of NOM, defined as the need for operative intervention, in patients who received early (< 48 h) or late LMWH (≥ 48 h, or early discharge [< 72 h] without LMWH).', 'We included 162 patients in our analysis. Most were men (69%), and the average age was 42 ± 18 years. The median injury severity score was 17, and splenic injuries were most common (97 [60%], median grade 2), followed by liver (57 [35%], median grade 2) and kidney injuries (31 [19%], median grade 1). Combined injuries were present in 14% of patients. A total of 78 (48%) patients received early LMWH, while 84 (52%) received late LMWH. The groups differed only in percent of high-grade splenic injury (14% v. 32%). Overall 2% of patients failed NOM, none after receiving LMWH. Semielective angiography was performed in 23 (14%) patients. The overall rate of confirmed VTE on imaging was 1.9%.'] Is very early initiation of chemical venous thromboembolism prophylaxis after blunt solid organ injury safe?