Efficacy of low-dose, subcutaneously administered heparin in treatment of pregnant women with artificial heart valves.

Between 1979 and 1982, the efficacy of fixed low-dose heparin, administered subcutaneously as thromboembolic prophylaxis, was studied during 14 pregnancies in 10 patients with mechanical heart valves. Calcium heparin (5000 units every 12 hours) was substituted for warfarin during the first trimester and the last month of pregnancy. Although the regimen was well tolerated and was associated with only 14% of first-trimester abortions, five episodes of thromboembolism occurred in four patients. Thus, this fixed, low-dose heparin regimen did not provide adequate thromboembolic prophylaxis in patients with prosthetic heart valves during pregnancy.