Platelet function in pregnant women receiving aspirin and dipyridamole

Abstract

Purpose. This study was undertaken to evaluate the hemostasis and coagulation profile of pregnant women receiving antiplatelet therapy with low-dose aspirin and dipyridamole for prevention of preeclampsia, intrauterine growth retardation, or pregnancy losses.

Methods. Twenty-three pregnant women who received antiplatelet therapy with combined aspirin (40 mg·day⁻¹) and dipyridamole (150 mg·day⁻¹) were enrolled in the study. Platelet aggregation and coagulation tests were performed before the start of aspirin and dipyridamole, during medication, and at 3 days and 6 days after cessation of medication.

Results. Collagen-induced platelet aggregation was decreased during medication (25 ± 26%, P < 0.001) and at 3 days after cessation of medication (46 ± 35%, P < 0.001) compared with that before the start of medication (89 ± 7%). ADP-induced platelet aggregation was decreased during medication compared with that before medication (66 ± 18% vs 92 ± 7%, P < 0.001). The platelet count, prothrombin time, activated partial thromboplastin time, bleeding time, and levels of fibrinogen and antithrombin III did not change over time. The blood loss of these patients during vaginal delivery and cesarean section did not differ from that of normal women during vaginal delivery and repeat cesarean section, respectively.

Conclusion. At the doses used in this study, aspirin and dipyridamole inhibited platelet aggregation for up to 3 days after cessation of medication. This abnormality of aggregation was not detected by the bleeding time and was not associated with clinically abnormal bleeding.