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-and continuous-wave Doppler at the aortic valve. Left ventricular chamber size, wall thickness, and mass were determined by M-mode echocardiography. Ventricular diastolic function was assessed by Doppler recording of mitral inflow. RESULTS: Cardiac output by pulsed Doppler increased 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 increased 18%. Left ventricular mass increased because of an increase in wall thickness. Peak mitral A wave velocity increased in late pregnancy. Cardiac output by pulsed and continuous-wave Doppler was similar. CONCLUSION: 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 compliance or increased preload.