Neonatal morbidity in early-onset fetal growth restriction with and without anticoagulant therapy.

Background: The study aims to evaluate the effectiveness of low molecular weight heparin (LMWH) in reducing neonatal morbidity in pregnancies with early-onset fetal growth restriction (FGR).

Methods: A phase III, multicenter, triple-blind, parallel-arm randomized clinical trial conducted in two university hospitals in Spain. Singleton pregnancies with early-onset placental FGR (20 + 0-31 + 6 weeks at diagnosis) were randomized to receive bemiparin (3500 IU/0.2 mL/day) or placebo from diagnosis to delivery. The primary neonatal outcome was morbidity up to hospital discharge, assessed using the Morbidity Assessment Index for Newborns (MAIN) score. Analyses followed an intention-to-treat approach.

Results: Fifty patients were randomized (25 per arm), with 49 included in the final analysis (23 LMWH, 26 placebo). Median gestational ages at inclusion were 28.7 weeks (LMWH) and 28.4 weeks (placebo). No significant differences were observed in MAIN scores between groups (171.5 vs. 290; p = 0.887; adjusted median difference 139.1 [95% CI -88.4 to 319.8]). NICU stay lengths were also similar (9 vs. 6.5 days; p = 0.738; adjusted median difference 1.08 [95% CI -0.74 to 13.4]).

Conclusion: Prophylactic LMWH started at diagnosis of early-onset FGR does not decrease neonatal morbidity or NICU stay duration.

Impact: Prophylactic LMWH started at the diagnosis of early-onset FGR does not decrease neonatal morbidity or NICU stay duration. Its design is a randomized, triple-blind clinical trial, which provides high-quality evidence. LMWH is often prescribed during pregnancy for various indications, and in the absence of effective alternatives, it is increasingly used empirically in such cases. Our findings do not support its use for reducing perinatal morbidity or NICU admission duration.