At 6 months postpartum, there was a sig- ni cant reduction in mean bone density (P 5 .02) and two of the 14 patients evaluated (14%) had The second study was an open randomized trial that included 44 pregnant women with VTE. Patients were assigned to either prophylactic doses of LMWH (dalteparin; n 5 21) once daily subcuta- neously or UFH (n 5 23) twice daily subcutane- ously during pregnancy and the puerperium. Dual x-ray absorptiometry of the lumbosacral spine was performed at 1, 6, 16, and 52 weeks. A healthy untreated control group was included for compar- ison. Mean bone density of the lumbar spine was signi cantly lower in the UFH group than in the dalteparin or control groups. Bone density measure- ments did not differ between the dalteparin and The third clinical trial compared the effects of long-term treatment with LMWH (enoxaparin) and acenocoumarol on bone mineral density in 86 patients with VTE. Treatment was given for 3 to 24 months. At 1 and 2 years of follow-up, the mean decrease in bone density of the femur was 1.8% and 2.6% in patients given acenocoumarol and 3.1% and 4.8% in patients given enoxaparin, respectively. These differences were not statistically signi cant.190 A recent review con rms that the strength of the association between LMWH and osteoporosis In summary, both UFH and LMWH preparations have the potential to produce osteopenia. The risk is lower with LMWH. 2012 American College of Chest Physicians by Kimberly Henricks on February 10, 2012 chestjournal.chestpubs.org Downloaded from e34S Parenteral Anticoagulants Heparin and LMWH can cause urticarial skin reac- tions. Rarely, skin necrosis can occur at sites of injec- tion. In these cases, HIT should be suspected. 