Background: The aim of this study was to assess the effect of long-term low molecular weight heparin (LMWH) on bone mineral density (BMD) during pregnancy.
Methods: Fifty-five patients with recurrent miscarriage and known thrombophilia (antiphospholipid syndrome) were followed through pregnancy in an ethically approved prospective observational study. All women had dual energy X-ray absorptiometry (DEXA) scans at the lumbar spine (L1-L4) performed within 6 months prior to conception and in the immediate post-natal period, within 6 weeks of delivery. LMWH (5000 U/day) plus low-dose aspirin was commenced after a positive urine pregnancy test and continued throughout pregnancy and after delivery until 6 weeks post-partum. A group of 20 volunteers with recurrent miscarriage, not requiring any treatment intervention, acted as controls and were monitored in an identical fashion.
Results: Characteristics were not significantly different between treated patients and controls. Both groups showed a similar loss in lumbar spine (L1-L4) BMD by the end of the pregnancy [LMWH 4.17% or 0.045 g/cm(3), 95% confidence interval (CI) 0.036-0.062 versus control 3.56% or 0.043 g/cm(3), 95% CI 0.027-0.059]. However, the difference in bone loss between the groups was not statistically significant (0.002 g/cm(3), CI -0.0124 to 0.00865; P = 0.88). No patient suffered vertebral fracture.
Conclusions: Bone loss associated with the use of long-term LMWH is not significantly different from physiological losses during pregnancy.