Objective: To assess the secondary preventive effect of low-molecular-weight heparin (LMWH) on pregnant women with prior early-onset or severe preeclampsia (PE).Methods: A systematic literature search of several databases was conducted for randomized controlled trials comparing LMWH with either aspirin or no treatment in pregnant women at a high risk of placental-mediated pregnancy complications (PMPCs). Odds ratios and associated 95% confidence intervals (CI) and weighted mean differences and 95% CI were calculated.Results: Seven studies including 1035 patients were evaluated. These studies showed a risk reduction in composite PMPC outcome (relative risk (RR) 0.635 (95% CI: 0.436-0.925); p=.018), PE (RR 0.522 (95% CI: 0.334-0.815); p=.004), a small-for-gestational-age neonate (RR 0.622 (95% CI: 0.440-0.880); p=.007), and an increase in gestational length (SMD 0.312 (95% CI: 0.017-0.607); p=.038) and neonatal weight (SMD 0.428 (95% CI: 0.066-0.791); p=.020).Conclusions: LMWH has a secondary preventive effect on early or severe PE and improves neonatal outcomes. In the future, additional large multicenter studies will need to focus on high-risk PE groups by more accurate screening to obtain more information before clinical application.
Keywords: High-risk; LMWH; PMPC; meta-analysis; preeclampsia.