title: Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves.
abstract: BACKGROUND
  Pregnancy 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  We 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%).
  
  
  CONCLUSIONS
  While 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.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC 27710, USA. andra.james@duke.edu
authors.forename: Andra H
authors.initials: AH
authors.lastname: James
authors.forename: Leo R
authors.initials: LR
authors.lastname: Brancazio
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Gehrig
authors.forename: Andrew
authors.initials: A
authors.lastname: Wang
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Ortel
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006350:Heart Valve Prosthesis; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects / Q000627:therapeutic use*; D006801:Humans; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000188:drug therapy*; D012306:Risk; D013927:Thrombosis / Q000453:epidemiology / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight