Cardiovascular hemodynamics in pregnancy. 3. Cardiac rate, stroke volume, total peripheral resistance, and central blood volume in multiple pregnancy. Synthesis of results.

Abstract

Abstract 1. 1. Changes in cardiac rate, stroke volume, total peripheral resistance, mean circulation time (arm-to-thigh), and central blood volume in single and multiple pregnancies are reported. 2. 2. Mean cardiac rate (15 per cent increase), mean cardiac stroke volume (30 per cent increase), and mean circulation time (16 per cent increase) changed in the same direction and approximately to the same degree in both single and twin pregnancy. 3. 3. Changes in mean total peripheral resistance (31 per cent decrease) and mean central blood volume (29 per cent increase) in twin pregnancy were approximately 10 per cent greater than in corresponding stages of single pregnancy. In both single and twin pregnancy, the central blood volume was an ever-decreasing fraction of total maternal blood volume as pregnancy progressed. 4. 4. An interpretation of the effects of pregnancy on cardiovascular hemodynamics is presented.