Generalized idiopathic osteoporosis and transient osteoporosis of the hip are both rare complications of pregnancy. More frequently, long-term heparin administration to treat deep thrombosis in the legs or pelvis may lead to substantial decreases in bone mass and consequently increased risk of osteoporosis. Therapeutic studies with the aim to counteract the osteoporosis inducing effect of heparins, have not been published to date. In the special situation of pregnancy, most medications used for osteoporosis are contraindicated. In our open randomised study, 9 women on heparin-treatment received daily 6.46 g of the bone preparation OHC (ossein-hydroxyapatite-compound) over a period of 6 months and were compared to 11 women without bone protective treatment. In the OHC-group, good compliance was observed with no side effects and reduced back pain. Bone mass did not change significantly, whilst it dropped significantly statistically in the controls.