A LONGITUDINAL-STUDY OF CARDIAC-OUTPUT IN NORMAL HUMAN-PREGNANCY

OBJECTIVE: Our purpose was to investigate the maternal hemodynamic and cardiac structural changes that occur during pregnancy. STUDY DESIGN: Eighteen women underwent serial echocardiography beginning at 8 to 11 weeks' gestation, then at monthly intervals throughout pregnancy and at 6 and 12 weeks post partum. Cardiac output was measured by pulsed-a nd continuous-wave Doppler at the aortic valve. Left ventricular chamb er size, wall thickness, and mass were determined by M-mode echocardio graphy. Ventricular diastolic function was assessed by Doppler recordi ng of mitral inflow. RESULTS: Cardiac output by pulsed Doppler increas ed from 6.7 +/- 0.9 L/min at 8 to 11 weeks' gestation to 8.7 +/- 1.4 L /min at 36 to 39 weeks' gestation before failing to 5.7 +/- 0.7 L/min 12 weeks post partum. Heart rate increased 29%, and stroke volume incr eased 18%. Left ventricular mass increased because of an increase in w all thickness. Peak mitral A wave velocity increased in late pregnancy . Cardiac output by pulsed and continuous-wave Doppler was similar. CO NCLUSION: Cardiac output continues to increase even in late pregnancy. Left ventricular mass increases because of increased wall thickness. The mitral flow velocity findings suggest decreased ventricular compli ance or increased preload.