Is the monitoring of anti-Xa activity necessary in pregnant women undergoing thromboprophylaxis?

Thromboprophylaxis is increasingly advocated in pregnancy for certain clinical conditions. Low molecular weight heparins offer potential benefit over unfractionated heparins with increased bioavailability and a longer half-life, thus allowing for once daily administration. This study aims to determine if monitoring of anti-Xa activity is necessary in pregnant women undergoing thromboprophylaxis. Twenty-five pregnancies were prospectively followed where either tinzaparin or enoxparin was employed for thromboprophylaxis. Once the anti-Xa levels were in the thromboprophylactic range (0.03-0.5 U/ml) no patient required a change of dose. Frequent monitoring of Anti-Xa levels, once in the thromboprophylactic range, may not be required.