HAZARDS OF HEPARIN - ALLERGY, HEPARIN-INDUCED THROMBOCYTOPENIA AND OSTEOPOROSIS

Heparin is the commonest mode of thromboprophylaxis used in pregnancy. It does not cross the placenta but has potential adverse effects on t he mother, of which the most important is heparin-induced osteoporosis . The hazards of heparin, including bleeding, skin reactions, heparin- induced thrombocytopenia and osteoporosis are discussed and the releva nt literature reviewed. Low-molecular-weight heparins have certain adv antages over standard unfractionated heparins, especially in obstetric s. Their longer half-life and increased bioavailability enable once-da ily injections, making them more convenient and acceptable. They are a s effective as standard heparin but have a theoretically more favourab le side-effect profile, providing less anticoagulant relative to antit hrombotic activity. Current evidence suggests a lower incidence of hep arin-induced thrombocytopenia. A reduced risk of osteoporosis is sugge sted but not yet proven. Although thrombo-embolism is currently the le ading cause of maternal mortality in the UK, antenatal heparin prophyl axis is not given to all women with previous thrombo-embolism because of continued fears concerning heparin-induced osteoporosis. A protocol is presented with guidelines for different levels of obstetric prophy laxis depending on the perceived level of risk.