Cardiac output increases independently of basal metabolic rate in early human pregnancy

Early pregnancy is characterized by the institution of a high-flow low-resi stance circulation. In this study, we tested the hypothesis that these hemo dynamic changes develop independently of changes in basal metabolic rate. I n 12 healthy women, we determined and calculated once during the follicular phase (day 5 +/- 2) and at 6, 8, 10, and 12 wk of pregnancy the following variables: body weight and length, body mass index, fat-free mass (FFM), me an arterial pressure (MAP), heart rate (HR), stroke volume, cardiac output (CO), total peripheral vascular resistance (TPVR), resting energy expenditu re (REE), FFM REE (REEFFM), and respiratory quotient (RQ). At 6 wk of gesta tional age, HR and CO had increased, whereas MAP and TPVR had decreased. Th ese changes persisted throughout the study period. Meanwhile, REE, REEFFM, RQ, FFM, and body weight did not change consistently. The changes with preg nancy in hemodynamics did not correlate with those in basal metabolic rate. In early pregnancy, the institution of a high-flow low-resistance circulat ion develops without a concomitant rise in basal metabolic rate. These find ings support the concept that the hemodynamic changes in early pregnancy de velop independently of concomitant changes in basal metabolic rate.