Cardiac output and the recumbent position in late pregnancy

Changes in cardiac output were measured by transcutaneous aortovelography in 30 pregnant patients and in 30 control subjects with change of position from the supine. When compared to the supine position, the left and right lateral and left 15 degrees tilt positions caused statistically significant increases in cardiac output, whereas the right 15 degrees tilt position did not. Neither fetal head engagement nor the time spent in each position had significant effects on the changes in cardiac output. It was not possible to identify a subgroup of pregnant patients who were particularly sensitive to changes in posture.