Thromb Haemost 2004; 92(04): 747-751
DOI: 10.1160/TH04-06-0337
Review Article
Schattauer GmbH

Low molecular weight heparin for the prophylaxis of thromboembolism in women with prosthetic mechanical heart valves during pregnancy

Betul Oran
1   Department of Medicine, Boston University Medical Center, Boston, Massachusetts, USA
,
Aviva Lee-Parritz
2   Department of Obstetrics/Gynecology, Boston University Medical Center, Boston, Massachusetts, USA
,
ack Ansell
1   Department of Medicine, Boston University Medical Center, Boston, Massachusetts, USA
› Author Affiliations
Further Information

Publication History

Received 01 June 2004

Accepted after resubmission 27 July 2004

Publication Date:
06 December 2017 (online)

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Summary

Increased thromboembolic events occur in women with mechanical prosthetic valves during pregnancy, and selecting an effective and safe anticoagulant is still a challenge. Low molecular weight heparin (LMWH) is a promising alternative, but a recent warning and label change about its use in patients with mechanical prosthetic valves has caused confusion among physicians. The aim of the present study was to review the risks of maternal and fetal complications with mechanical heart valves treated with LMWH during pregnancy. We performed a review of the current medical literature through MEDLINE and EMBASE (1989 to 2004). Additional data sources included abstract proceedings, and reference lists of selected articles. Among 81 pregnancies in 75 women, the proportion of valve thrombosis was 8.64% (7/81; 95% CI, 2.52%–14.76%). The frequency of overall thromboembolic complication (TEC) was 12.35% (10/81; 95% CI, 5.19%–19.51%). Nine of ten patients with TEC received a fixed dose of LMWH and two of these received a fixed low dose of LMWH. Among 51 pregnancies whose anti-factor Xa levels were monitored, only one patient was reported to have a thromboembolic complication. The frequency of live births with LMWH was 87.65% (95%CI, 80.49%94.81%). In pregnant women with mechanical heart valves, LMWH appears to be a suitable option to a vitamin K antagonist. The use of LMWH warrants monitoring and appropriate dose adjustments to maintain a 4–6 hr post-injection anti-factor Xa level at a minimum of 1.0 U/ml to decrease the incidence of TEC.