Low-molecular-weight heparins in pregnancy may cause less bone loss

OB/GYN News,  Feb 1, 2003  by Jeff Evans

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NEW ORLEANS -- The antithrombotic low-molecular-weight heparins may cause less osteoporosis during pregnancy than unfractionated heparins, according to Dr. Munther Khamashta.

He reviewed all of the available literature on osteopenia and osteoporosis in pregnancy caused by antithrombotic agents. One review article of antithrombotic agents during pregnancy noted that a reduction of bone mineral density occurs in up to 30% of pregnant women receiving unfractioned heparin (UH), causing symptomatic vertebral fractures in 2%-3% of such women, he said at the Third International Conference on Sex Hormones, Pregnancy and the Rheumatic Diseases.

The use of the low-molecular-weight heparins (LMWHs) dalteparin, enoxaparin, nadroparin, reviparin, and tinzaparin resulted in only one vertebral fracture in 486 pregnancies at 21 centers in one study reviewed. A French retrospective study of enoxaparin in 624 pregnancies did not show any osteoporotic fractures.

His experience with dalteparin from 1992 to 1995 at the Lupus Research Unit at St. Thomas Hospital, London, involved one woman with osteoporosis out of 32, possibly due to overtreatment with the agent, he said at the conference, also sponsored by the University of Connecticut and the University of Utah.

The only randomized study comparing UH with LMWH showed that both 21 women who received dalteparin and 19 control women had significantly higher bone mineral density than 23 women who received UH at 1, 6, 16, and 52 weeks after delivery All of the women were treated for approximately 200 days and were given calcium and vitamin D supplements (Thromb. Haemost. 87[2]:182-86, 2002).

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