Sixteen obstetric patients with pulmonary artery catheters were studied by two-dimensional and pulsed Doppler echocardiography to compare prospectively pulsed Doppler-and thermodilution-derived estimations of left ventricular stroke volume and cardiac output. Systolic aortic flow velocity waveforms were obtained by pulsed Doppler ultrasound from the apical five-chamber echocardiographic window. Aortic diameters were obtained by two-dimensional echocardiography from the left parasternal long axis view. The mean (+/- SEM) aortic diameter averaged 2.1 +/- 0.1 cm, with a mean calculated aortic valve area of 3.6 +/- 0.2 cm2. The mean aortic flow velocity integral was 21.8 +/- 0.8 cm. This information was used to calculate aortic stroke volume and cardiac output. Thermodilution- and Doppler-derived estimations for maternal stroke volume (r = 0.86) and cardiac output (r = 0.94) were significantly correlated when aortic diameter measurements based on a leading vessel edge method were used. Our findings verify the accuracy of an important noninvasive technique for quantitating maternal stroke volume and cardiac output by pulsed Doppler echocardiography. This methodology should provide an alternative approach to invasive monitoring in the study of normal and abnormal maternal circulatory hemodynamics.