Background
Phase 3, open-label, multicenter RCT (ALIFE2). 839 women with unexplained recurrent miscarriage (≥3 consecutive miscarriages before 20 weeks, no anatomical, genetic, or antiphospholipid antibody cause identified) at 26 hospitals in the Netherlands, Belgium, and UK. All women received low-dose aspirin; randomized to add LMWH or not. Prior to this trial, LMWH was widely used off-label in this setting based on observational data and proposed prothrombotic mechanisms.
Interventions and follow up
Arm A: LMWH (nadroparin, dalteparin, or enoxaparin — dose equivalent to prophylactic dose) + low-dose aspirin 80 mg daily, started ≤6 weeks gestation, continued until 36 week
Arm B: Low-dose aspirin 80 mg daily alone (no LMWH)
Primary endpoint: Live birth rate (birth of a live child at ≥24 weeks gestation)
mFollow up: Delivery
Arm B: Low-dose aspirin 80 mg daily alone (no LMWH)
Primary endpoint: Live birth rate (birth of a live child at ≥24 weeks gestation)
mFollow up: Delivery
Results
Live birth rate: 74.4% (LMWH + aspirin) vs 75.0% (aspirin alone), RR 0.99 (95% CI 0.93–1.06), P=.81 — NS
Miscarriage: 19.2% vs 18.5% — similar
Preterm birth <37 weeks: 7.8% vs 6.3% — similar
Preeclampsia: 3.3% vs 2.3% — similar
Miscarriage: 19.2% vs 18.5% — similar
Preterm birth <37 weeks: 7.8% vs 6.3% — similar
Preeclampsia: 3.3% vs 2.3% — similar
Adverse events
Main adverse events: Injection-site reactions and minor bleeding more common with LMWH (as expected). No major bleeding episodes. DVT/PE similar between arms.
Conclusions
Adding LMWH to low-dose aspirin did not improve live birth rates in women with unexplained recurrent miscarriage, providing definitive evidence against routine LMWH use in this common and distressing condition.
Key Limitations
Key Limitations: Open-label design (blinding of LMWH injection not feasible). All patients received aspirin — the independent effect of aspirin itself was not tested. Results cannot be directly extrapolated to women with antiphospholipid syndrome (excluded) or inherited thrombophilia. Some patients in the control arm may have received LMWH from treating physicians (protocol violation risk). Psychosocial benefits of "doing something" are difficult to separate from pharmacological effects.
Clinical Context
ALIFE2, together with the earlier ALIFE trial, provides the most robust evidence against LMWH for recurrent miscarriage outside of established APS. Major society guidelines (RCOG, ASRM, ACOG) now recommend against routine LMWH in unexplained recurrent pregnancy loss. This has practical implications: LMWH is costly, burdensome, and carries bleeding risk, and prior widespread off-label use was not evidence-based.