Pulsed Doppler and M-mode maternal echocardiography were combined with uterine and umbilical artery Doppler velocimetry to characterize the hemodynamic changes associated with fluid preload and epidural anesthesia in 12 normal laboring gravidas at term. Fluid preload alone was associated with significant (P less than .05) increases in heart rate (11%), stroke volume (10%), and cardiac output (20%), and a decrease in systemic vascular resistance (19%). There were no changes in mean arterial pressure (MAP) or ejection fraction during any stage of the study. Following placement of the epidural block, stroke volume and cardiac output returned to values not significantly different from baseline, whereas heart rate remained elevated and systemic vascular resistance remained decreased. There were no changes in uterine or umbilical artery systolic-diastolic (S-D) ratios during any stage of the study. We conclude that fluid preload and epidural anesthesia cause significant changes in maternal cardiac output, heart rate, stroke volume, and systemic vascular resistance without affecting MAP. These maternal changes do not correlate with any changes in uterine or umbilical artery S-D ratios following epidural anesthesia in the normal laboring gravida.