Low molecular weight heparin (dalteparin) for the treatment of venous thromboembolism in pregnancy

Objective To evaluate the effect and dose of dalteparin given to pregnant women with acute venous thromboembolism. Design An observational study of pregnant women in Norway. Setting Delivery and haematological departments in Norway. Population Twenty women, aged 22-41 years, with acute venous thromboembolism verified by objective means. Methods Patients were treated with dalteparin from diagnosis until delivery. Treatment was monitored with anti-activated factor Xa (anti-Xa) activity, and the dose was adjusted to achieve target 0.5-1.0 U/mL 2-3 hours post-injection. Main outcome measure Anti-Xa activity and side effects. Result None of the patients suffered recurrent venous thromboembolism or major bleeding complications. In 9 of 13 women starting with conventional dose of dalteparin (100 iu/kg bd), dose escalation was necessary to reach target anti-Xa activity. None of the six women who started with 105-118 iu/kg bd required dose escalation. One woman who started with 133 iu/kg bd required dose reduction. Bioaccumulation of dalteparin was not observed. Conclusion Our study suggests that dalteparin may be used for the treatment of acute venous thromboembolism in pregnancy. Approximately 10-20% higher doses of dalteparin may be needed as compared with non-pregnant individuals.