A less-intensive anticoagulation protocol of therapeutic unfractionated heparin administration for pregnant patients

Heparin anticoagulant therapy for thromboembolic disorders during pregnancy is problematic due to unexpected adverse bleeding. To avoid bleeding, we have used a less-intensive anticoagulation protocol of unfractionated heparin (UFH). The protocol had a therapeutic activated partial thromboplastin time (APTT) ratio of 1.5-2.0 with the control value, a UFH dose of ≤ 30,000 U/day, and an antithrombin (AT) activity target of ≥ 70%. In the present study, we evaluated this protocol using an anti-Xa assay. We collected UFH-treated plasma samples from ten consecutive pregnant Japanese patients with current or previous thromboembolic disorders. Seven patients remained in the therapeutic APTT ratio range (heparin-sensitive [HS] group). The other three patients had difficulty remaining within the therapeutic range (heparin-resistant [HR] group). In the HR group, two had AT deficiency and one had congenital absence of the inferior vena cava. Of the HS and HR samples, 73% and 31%, respectively, were within the therapeutic anti-Xa activity range 0.3-0.7 U/mL, indicating difficulty for the HR group to remain within the therapeutic range. Neither major bleeding nor symptomatic thromboembolic episodes occurred in either group. These findings suggest that the less-intensive anticoagulation protocol is permissive and may be beneficial in the HS group.