Purpose of review: Osteoporosis is the most common serious side effect of long-term unfractionated heparin use. Until recently, it was unknown whether long-term low-molecular-weight heparin was associated with any change in bone mineral density. With increasing long-term low-molecular-weight heparin use, for a variety of indications, this was an important knowledge gap.
Recent findings: We recently completed an a-priori planned substudy to assess the effect of low-molecular-weight heparin on bone mineral density in an ongoing multicenter multinational randomized trial designed to compare the effect of low-molecular-weight heparin prophylaxis on pregnancy outcomes in thrombophilic pregnant women. The results revealed that there is no significant difference in mean bone mineral density between a low-molecular-weight heparin prophylaxis group and a no prophylaxis group. The study was not adequately powered to detect differences in absolute fracture risk.
Summary: Recent results suggest that the use of long-term prophylactic low-molecular-weight heparin in pregnancy is not associated with a significant decrease in bone mineral density. Whether higher doses might be a risk factor for osteoporosis is still an unanswered question. It is also possible that subgroups are more susceptible. Overall, women should be reassured regarding the risk of osteoporosis associated with the use of prophylactic dose of low-molecular-weight heparin during their pregnancy.