BACKGROUND: The role of progestogens in haemostasis is controversial. Our objective is to evaluate the haemostatic effects of an etonogestrel-releasing implant. METHODS: This open-label, self-controlled, longitudinal study involved 20 healthy women receiving subcutaneous etonogestrel-releasing implants. At baseline, 1, 3 and 6 months, we measured the following: activated partial thromboplastin time; prothrombin time; thrombin time; fibrinogen; coagulation factors II, V, VII, VIII, IX, X and XI;

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... von Willebrand factor; activated protein C (APC); antithrombin; free protein S; plasminogen activator inhibitor type 1 (PAI-1); a2-antiplasmin; thrombin-antithrombin (TAT) complex; prothrombin fragment 1 1 2 (F1 1 2); D-dimers; APC resistance. Statistical analyses included the Friedman test and ANOVA. RESULTS: Levels of APC (P < 0.01), factor II (P 5 0.02), factor VII (P 5 0.006), factor X (P 5 0.01) and F1 1 2 (P < 0.001) were reduced, whereas those of PAI-1 (P 5 0.01) and factor XI (P 5 0.006) were transitory increased. All of these values, however, remained within normal ranges. Surprisingly, TAT concentrations fell below the normal range (P < 0.001). CONCLUSIONS: Our findings suggest that the etonogestrelreleasing implant does not induce a prothrombotic pattern during the first six months of use, and that its use is associated with a reduction in thrombin generation.