Effects of posture on limb blood flow in late pregnancy.

Arm and leg blood flow was measured in 40 patients in late pregnancy in the supine and left lateral positions, and the changes were contrasted with changes found in 15 patients investigated in the early puerperium. A significant reduction in leg flow occurred in the pregnant subjects when the supine position was assumed. A further 30 patients in late pregnancy had leg flow measured in the following positions: left lateral, supine, right lateral, and the two mid-positions. Leg flow significantly increased on moving from the supine to all other positions except the right intermediate position, indicating that a leftward tilt is more effective in preventing caval compression.