Bone mineral density during long-term prophylaxis with heparin in pregnancy.

Objective: We studied the effect of long-term heparin treatment on bone mass during pregnancy.
Study Design: Thromboprophylaxis with heparin was given to 39 women during pregnancy for a mean of 28 weeks and for an average of 6 weeks post partum. Bone mineral density measured with single-photon absorptiometry of the distal and ultradistal parts of the forearm was determined at the time of the start of heparin treatment (mean, twelfth week of gestation), immediately post partum, and on average 7 weeks post partum. The mean dosage of heparin was 17,300 IU/day. A control group of 34 normal pregnant women was studied for comparison.
Results: In women treated with heparin, there was almost a 5% reduction in trabecular bone during pregnancy (p < 0.01) and an insignificant recovery post partum. There were no significant changes in bone mass during pregnancy or in the puerperium in the control group.
Conclusion: Long-term treatment with heparin during pregnancy is associated with bone loss, but indications of reversible changes are observed.