Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves.
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.
James
Andra H
AH
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC 27710, USA. andra.james@duke.edu
Brancazio
Leo R
LR
Gehrig
Thomas R
TR
Wang
Andrew
A
Ortel
Thomas L
TL
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*
D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight