Final answer:
The false statement about metabolic and cardiac adaptations to pregnancy is that heart rate is lower at rest and during submaximal exercise. In reality, pregnancy leads to a higher heart rate to support increased blood volume and metabolic demand. Blood volume increases by ~30%, and the metabolic rate remains stable or increases.
Step-by-step explanation:
The statement that is NOT true about the metabolic and cardiac adaptations to pregnancy is that 'heart rate is lower at rest and during submaximal exercise.' During pregnancy, the opposite occurs: heart rate actually increases to meet the higher metabolic demand and to support the increased blood volume.
Pregnancy results in substantial physiological changes to support the growing fetus. Maternal blood volume increases by about 30 percent to accommodate the needs of the fetus for nutrients and waste removal, which corresponds to approximately 1-2 liters of additional blood by childbirth. This increase in blood volume contributes, along with hormonal changes, to an increased heart rate and moderate rise in blood pressure. In the third trimester, there is a higher risk of arterial hypotension, not due to decreased cardiac output but rather because the expanding uterus can compress the underlying pelvic blood vessels, affecting venous return.
The metabolic rate during pregnancy does not decrease; instead, it stays constant or may increase slightly to support fetal development. This is evident in the increased appetite and possible experience of hot flashes due to an increase in thyroid hormone stimulated by placental hormones and thyrotropin.