LMWH During Pregnancy Preserves BMD


LISBON — Long-term treatment with low-molecular-weight heparin during pregnancy did not cause a drop in spinal bone mineral density in a study with 62 women.

Extended administration of low-molecular-weight heparin (LMWH) during pregnancy, as prophylaxis for thrombophilia, also did not produce a clinically important fracture risk, Dr. Marc A. Roger said at the third World Congress of the International Society of Obstetric Medicine.

In contrast, long-term treatment with unfractionated heparin during pregnancy often causes a drop in bone mineral density—frequently a clinically significant drop, said Dr. Roger, head of the thrombosis and hemostasis program at Ottawa Hospital. According to prior study results, up to 2.2% of women who have had prolonged exposure to unfractionated heparin during pregnancy develop osteoporotic fractures.

The new findings came from a prespecified subgroup analysis of data collected in the Thrombophilia in Pregnancy Prophylaxis Study (TIPPS), an ongoing, multicenter trial that was designed to compare prophylaxis using LMWH with placebo for pregnancy outcomes in women with a thrombophilia. The subanalysis was designed to assess the effect of LMWH on bone mineral density.

Both TIPPS and the bone mineral density subanalysis were sponsored by Pfizer, which markets dalteparin (Fragmin), the LMWH used in the studies. Dr. Roger has received research support from and is on a scientific advisory board for Pfizer.

TIPPS enrolled women with confirmed thrombophilia at less than 20 weeks' gestation who were at risk for thromboembolism or had a history of pregnancy complications. They were randomized to placebo or to 5,000 U dalteparin daily through week 20, followed by a regimen of 5,000 U b.i.d. through delivery. All women in the study received dalteparin post partum for 6 weeks.

In the substudy, which involved 62 women, the primary end point was the absolute lumbar-spine bone mineral density measured at 6 weeks post partum. Because of crossovers, 33 women received dalteparin and 29 women received placebo.

The average bone mineral density was 1.15 g/cm2 in the LMWH group and 1.20 g/cm2 in the control group, a difference that was not statistically significant. In addition, the 95% confidence interval for bone mineral density in the dalteparin group did not enter the range that defines osteopenia (less than one standard deviation below the mean).

Hence, “we can say with confidence that if low-molecular-weight heparin causes a difference in bone density, it's a small difference,” Dr. Roger said.

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