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A longitudinal study of cardiac output in normal human pregnancy
W C Mabie1, T G DiSessa, L G Crocker
1Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38103.
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 +/- 0.6 L/min at 8 to 11 weeks' gestation to 8.7 +/- 1.4 L/min at 36 to 39 weeks' gestation before falling 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 suggested decreased ventricular compliance or increased preload.