Early Prophylactic Enoxaparin for the Prevention of Preeclampsia and Intrauterine Growth Restriction: A Randomized Trial

Abstract

Background: Preeclampsia (PE) and intrauterine growth restriction (IUGR) are major causes of maternal and perinatal morbidity and mortality. Previous studies have shown that intervention with low-dose aspirin resulted in a reduction in the occurrence of preterm PE. However, no data are currently available on the effect of low-molecular-weight heparin (LMWH) for the prevention of pregnancy complications in women enrolled at first trimester screening. Objective: We aimed to assess the effectiveness of LMWH in the prevention of PE, IUGR, fetal death, and abruptio placentae in women classified as high risk based on their medical history and in women selected by first trimester screening of PE. Study ­Design: This was a multicenter, randomized, open-label, parallel controlled trial in women without thrombophilia between 6.0 and 15.6 weeks of gestation. Inclusion criteria were severe PE or IUGR before 34 weeks of gestation and/or abruptio placentae or unexplained intrauterine death in a previous pregnancy; uterine artery mean pulsatility index Doppler >95th percentile and/or positive first trimester screening for PE. Pregnant women were randomly assigned to receive no intervention or LMWH until the 36th week of gestation. The primary composite outcome consisted of 1 or more of the following: development of PE, IUGR, abruptio placentae, and intrauterine fetal death. Results: A total of 278 pregnant women were randomly allocated to receive LMWH (n = 134) or no intervention (n = 144). Overall, 115 (41%) women experienced placental insufficiency complications, with no significant differences between the 2 arms: 50/144 (34.7%) in the LMWH arm and 43/134 (32%) in the control arm (p = 0.64, OR: 1.13, 95% CI: 0.68–1.85). Conclusion: LMWH did not reduce the incidence of placenta-mediated complications either in women with previous adverse obstetric history without thrombophilia or in women selected by first trimester screening for PE. Based on these results, we cannot recommend the use of LMWH alone in women at risk of placental complications.