Prophylactic Low Molecular Weight Heparin (LMWH) during Pregnancy Is Not Associated with a Decrease in Bone Mineral Density (BMD). The TIPPS (Thrombophilia in Pregnancy Prophylaxis Study) BMD Substudy.

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Abstract
Background: Decreased BMD is a relatively common serious complication of long-term heparin use, however there have not been adequately powered randomized controlled trials addressing its risk in association with long-term use of LMWH. The TIPPS study is an ongoing multi-center randomized trial designed to compare the effect of LMWH prophylaxis vs. no prophylaxis on pregnancy outcomes in thrombophilic pregnant women. A separate sub-study was planned a priori to assess the effect of LMWH on BMD. Methods: Pregnant women (100 kg wt. Patients (pts) were randomized to either LMWH (dalteparin [dalt] 5,000 U qd until 20 wks and then 10,000 qd until term) or control (ctrl) group. All participants received post-partum dalt 5,000 U qd from postpartum d1 to d42. BMD (hip and lumbar spine) was performed 6 wk post-partum. A sample size of 26 pts per group was calculated to detect a 10% difference in absolute BMD (α=0.05, β=0.10). Primary outcome was absolute spine BMD compared using an unpaired t-test. Results were analyzed as-treated; 31 pts received dalt and 22 did not (4 pts randomized to ctrl group crossed over). Duration of dalt treatment was 214.5±41.9d for dalt group and 47±38.6d for ctrl (p<0.001). Two cases of osteoporosis (Opo) and 7 cases of osteopenia (Ope) were documented in the dalt group vs 0 of Opo and 3 of Ope in the ctrl group respectively. Results of post-hoc logistic regression analysis examining the odds of obtaining an abnormal (Opo or Ope) spine or hip BMD result in both treatment groups were non significant (Crude OR 2.59; 95%CI 0.61, 10.97; p=0.20; Adjusted OR 6.83; 95%CI 0.17, 272.33; p=0.307) as well as results of post-hoc multiple linear regression to predict changes in BMD and T-scores. Conclusion: Our results suggest that the use of long term prophylactic dalteparin in pregnancy is not associated with a significant decrease in BMD.

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