• Andra H James, Leo R Brancazio, Thomas R Gehrig, Andrew Wang, and Thomas L Ortel.
• Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC 27710, USA. andra.james@duke.edu
• J. Matern. Fetal. Neonatal. Med. 2006 Sep 1;19(9):543-9.

BackgroundPregnancy in a woman with a mechanical heart valve is a life-threatening situation. Due to the inability of unfractionated heparin to prevent valvular thromboses, warfarin or other vitamin K antagonists have been the preferred anticoagulants for the mother. They are, however, potentially harmful to the fetus. With the advent of low-molecular-weight heparins, clinicians were hopeful for an alternative that was safe for the fetus, but more effective than unfractionated heparin, which carries a 29-33% risk of life-threatening thromboses and a 7-15% chance of mortality. Unfortunately, fatal thromboses have occurred with low-molecular-weight heparin as well.MethodsWe searched the MEDLINE database and other sources to identify cases of the use of low-molecular-weight heparin for thromboprophylaxis in women with mechanical heart valves.ResultsWe found 73 cases and added three of our own for a total of 76. There were 17 thrombotic events (22%). Thirteen were valve thromboses, two were strokes, and two were myocardial infarctions. There were three deaths (4%).ConclusionsWhile pregnant women with mechanical heart valves who receive low-molecular-weight heparin for thromboprophylaxis are at extremely high risk of life-threatening thromboses, there is no evidence that low-molecular-weight heparin is inferior to unfractionated heparin.

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