In the E-MOTIVE trial (2023, Lancet), a bundle intervention for postpartum haemorrhage (PPH) was tested against standard care. The bundle comprised uterine massage, oxytocin, tranexamic acid, examine and treat, and calling for help (if needed). The primary outcome (severe PPH defined as blood loss ≥1 litre) was significantly reduced. What is the mechanism by which tranexamic acid reduces blood loss in PPH when administered within 3 hours of delivery?

• A Direct uterotonic effect by stimulating oxytocin receptors in the myometrium
• B Inhibition of plasminogen activators, preventing fibrinolysis of formed clot ✓
• C Inhibition of thromboxane synthetase, increasing prostacyclin-mediated vasoconstriction
• D Reduction in factor Xa activity, decreasing clot formation rate

Explanation

Tranexamic acid is a lysine analogue that competitively inhibits plasminogen activators (tissue plasminogen activator and urokinase), preventing the conversion of plasminogen to plasmin and thereby preserving fibrin clot integrity at bleeding sites — this is antifibrinolytic activity, not pro-coagulant activity. The WOMAN trial (2017) first demonstrated that tranexamic acid reduces PPH mortality when given within 3 hours. It has no direct uterotonic, thromboxane, or factor Xa effects.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.