Postpartum venous thromboembolism prophylaxis may cause more harm than benefit: a critical analysis of international guidelines through an evidence‐based lens

Based on prediction models and expert opinion, most obstetric venous thromboembolism guidelines recommend low-molecular-weight heparin for many postpartum women, including most delivering by caesarean. Scrutiny reveals major oversights: prediction models are based on studies that report asymptomatic deep vein thrombosis; risk estimates are not adjusted for time exposure; and harm caused by heparin has been overlooked. The benefits of heparin are exaggerated and its harms are under-appreciated. Estimates of the numbers-needed-to-treat and harm are universally lacking. This paper critically reviews the evidence and quantifies the benefit and harm from low-molecular-weight heparin in postpartum women with common risk factors. FUNDING: This work was unsponsored and unfunded. TWEETABLE ABSTRACT: Randomised trials should demonstrate more benefit than harm before widespread postpartum low-molecular-weight heparin is recommended.