Heparin is an injectable blood thinner. Doctors sometimes prescribe it to women with antiphospholipid syndrome or other blood-clotting disorders that are linked to recurrent pregnancy loss.
Recurrent miscarriage can have a number of causes, and some are more well understood than others. One medical factor doctors agree upon in recurrent miscarriages is thrombophilia disorders, or medical conditions in which the blood has an increased tendency to clot (such as antiphospholipid syndrome).
In thrombophilia disorders, researchers believe that tiny clots get stuck in the developing placenta, blocking flow of nutrients to the baby and eventually causing miscarriage (or increasing risk of other pregnancy complications, such as pre-eclampsia).
For women with diagnosed thrombophilia conditions and recurrent miscarriages, a common treatment is heparin -- often alongside low-dose "baby" aspirin. Heparin works by thinning the blood and decreasing the tendency to form clots.
Using heparin during pregnancy is not without risk; the drug can have side effects in some people and may increase the risk of bone loss or tendency to hemorrhage. However, studies have found that using heparin for women with disorders like antiphospholipid syndrome improves pregnancy outcomes.
Researchers are investigating whether heparin may improve pregnancy rates for women with multiple miscarriages and no diagnosed thrombophilia condition, but this use of heparin should be considered experimental. Because of the notable risks of using heparin, most practitioners recommend heparin only in women with a history of pregnancy problems and a confirmed thrombophilia diagnosis. Expanded recommendations are not likely in the near future, if ever.
Sources:
Di Nisio, M., L.W. Peters, S. Middeldorp, "Aspirin or anticoagulants for the treatment of recurrent miscarriage in women without antiphospholipid syndrome. Cochrane Library 2008. Accessed 29 Feb 2008.
Empson, M., M. Lassere, J. Craig, and J. Scott, "Prevention of recurrent miscarriage for women with antiphospholipid antibody or lupus anticoagulant." Cochrane Library. 2008. Accessed 29 Feb 2008.
March of Dimes, "Thrombophilias and Pregnancy." Quick Reference: Fact Sheets. Oct 2006. Accessed 29 Feb 2008.
