['To determine whether prothrombin is present in follicular fluid and whether the enzymatic pathways for prothrombin activation are similar to those in plasma.', 'Follicular fluid samples collected at the time of oocyte harvest for an assisted reproductive technology procedure (ART) were analyzed for a panel of hemostatic proteins with use of a combination of functional, chromogenic, and Western ligand blot analysis.', 'An ART clinic and an academic research laboratory.', 'Women undergoing ART.', 'None.', 'Determination of components of thrombin generation and thrombin modulatory systems using functional and antigenic assay procedures.', 'Both prothrombin and components of the prothrombinase enzyme complex, which includes factors V, VII, and X, are present in follicular fluid. Other hemostatic proteins, including factors VIII and IX and vonWillebrand factor, are absent. The direct activation of prothrombin to thrombin is similar in follicular fluid and plasma. Like plasma, inhibitors of both thrombin and thrombin generation, including antithrombin, protein C, and alpha2-macroglobulin, are present in follicular fluid.'] Does human ovarian follicular fluid have functional systems for the generation and modulation of thrombin?