OBJECTIVE To compare values for two whole blood viscoelastic coagulation tests, thromboelastography (TEG) and Sonoclot analysis (Sonoclot R Coagulation Analyzer, Sienco, Inc., Morrison, CO), between healthy parturients and nonparturients. METHODS Prospective study. METHODS University hospital. METHODS 41 healthy, nonpregnant females and full-term nonlaboring and laboring parturients. METHODS Blood samples for TEG and Sonoclot analysis were taken from all patients. TEG tracings were analyzed for reaction time (R), coagulation time (RK), the difference between RK and R (K), clot formation rate (alpha degree), and maximum amplitude (MA) values. Sonoclot tracings were analyzed for onset, rate increases, peak, and rate decreases values. RESULTS All TEG values were significantly different between nonpregnant females and parturients (p < 0.05). Sonoclot analysis showed that the parturients had a significantly decreased onset and increased primary slope (rate increases) in comparison to the nonpregnant females (p < 0.05). CONCLUSIONS The differences found in the parturients reflect a hypercoagulable state. If these tests are to be used in evaluating obstetric patients, the results should be compared with values obtained for healthy parturients, not healthy nonparturients.