Low-molecular-weight heparin (LMWH) is commonly used for preventing or treating venous thromboembolic disease (VTE) during pregnancy. The physiological changes in maternal metabolism have led to discussions on optimal LMWH dosing strategy and possible need for monitoring. The aim of this systematic review is to summarize and discuss whether LMWH dose adjustment according to anti-Xa provides superior effectiveness and safety compared with weight adjusted or fixed dosed LMWH in pregnant women. A systematic literature search was performed in PubMed, Embase, and Scopus on September 26, 2020. The study is reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Effectiveness was defined as episodes of thrombosis and safety as bleeding episodes. In total, 33 studies were included: 4 randomized controlled studies and 29 cohort studies. Prophylactic dosing strategies employing weight dosed, fixed dosed, or anti-Xa adjusted LMWH dosing performed equal in effectiveness and safety. In pregnant women with VTE or high thromboembolic risk, therapeutic weight–adjusted LMWH and weight plus anti-Xa-adjusted LMWH provided equal results in terms of effectiveness and safety. Pregnant women with mechanical heart valves (MHVs) received therapeutic anti-Xa-adjusted LMWH with four out of seven studies presenting mean peak anti-Xa within target ranges. Still, pregnant women with MHV experienced both thrombosis and bleeding with anti-Xa in target. Based on the results of this systematic review, current evidence does not support the need for anti-Xa monitoring when using LMWH as thromboprophylaxis or treatment during pregnancy. Nonetheless, the need for anti-Xa monitoring in pregnant women with MHV may need further scrutiny.

低分子肝素（LMWH）通常用于预防或治疗妊娠期静脉血栓栓塞性疾病（VTE）。母体代谢的生理变化引发了关于最佳 LMWH 给药策略和可能需要监测的讨论。本系统评价的目的是总结和讨论与体重调整或固定剂量的 LMWH 相比，根据抗 Xa 调整 LMWH 剂量是否在孕妇中提供更好的有效性和安全性。2020 年 9 月 26 日在 PubMed、Embase 和 Scopus 中进行了系统的文献检索。该研究是根据系统评价和元分析的首选报告项目 (PRISMA) 指南报告的。有效性定义为血栓形成事件，安全性定义为出血事件。共纳入 33 项研究：4 项随机对照研究和 29 项队列研究。采用体重剂量、固定剂量或抗 Xa 调整的 LMWH 剂量的预防性剂量策略在有效性和安全性方面表现相同。在有 VTE 或高血栓栓塞风险的孕妇中，治疗性体重调整 LMWH 和体重加抗 Xa 调整 LMWH 在有效性和安全性方面提供了相同的结果。具有机械心脏瓣膜 (MHV) 的孕妇接受了治疗性抗 Xa 调整的 LMWH，七项研究中有四项显示平均峰值抗 Xa 在目标范围内。尽管如此，患有 MHV 的孕妇在靶向抗 Xa 的情况下同时经历了血栓形成和出血。根据该系统评价的结果，目前的证据不支持在妊娠期间使用 LMWH 作为血栓预防或治疗时需要进行抗 Xa 监测。尽管如此，