Placental Pathological Findings following Adjusting Enoxaparin Dosage in Thrombophilic Women: Secondary Analysis of a Randomized Controlled Trial

Abstract

Objective: Randomized trials showed no improvement in pregnancy outcomes with the use of low molecular weight heparin (LMWH) to prevent placenta-mediated pregnancy complications (PMPCs) among thrombophilic women. However, the effect of treatment on placental findings was not examined. We aimed to examine the occurrence of placental vascular lesions in thrombophilic women treated with LMWH dose adjusted according to anti-factor Xa compared with a fixed dose.

Study design: This study was a secondary analysis of a randomized trial designed to examine whether LMWH dose adjusted according to anti-factor Xa levels compared with a fixed dose would reduce the risk of PMPC. Eligible women were randomly allocated in a 1:1 ratio to either a fixed dose of 40 mg daily LMWH (fixed dose group) or adjusted dose according to anti-factor Xa levels (adjusted dose group). Placentas were examined by the same perinatal pathologist who was blinded to group allocation. The primary outcome for this analysis was the incidence of maternal placental vascular lesions.

Results: During the study period, 88 placentas were examined; 41 and 47 from the fixed and adjusted dose groups, respectively. Demographics, obstetrics and types of thrombophilias were similar between the groups. Maternal placental vascular lesions were observed in 23 (56.1%) and 21 (44.68%) placentas (p = 0.28) and foetal placental vascular lesions in 2 (4.88%) and 1 (2.13%) placentas (p = 0.59) in the fixed and adjusted groups, respectively.

Conclusion: Adjusted dose of enoxaparin according to anti-factor Xa levels compared with a fixed dose did not affect placental vascular lesions in thrombophilic women.