Final answer:
During pregnancy, cardiac output increases by approximately 30-50% to meet the increased demands of the fetus and to manage the increased maternal blood volume. This increase is facilitated by changes in heart rate and stroke volume, akin to the body's response to exercise.
Step-by-step explanation:
Cardiac output (CO), which is the volume of blood the heart pumps per minute, increases significantly during pregnancy. This change is necessary to support the growing fetal demand as well as to manage the increased maternal blood volume efficiently. During pregnancy, the cardiac output can increase by approximately 30-50%. Blood volume itself increases by about 30% or roughly 1-2 liters, which in combination with other factors, contributes to the rise in CO.
For a more detailed understanding, the heart rate (HR) and stroke volume (SV) —the amount of blood pumped out by a ventricle with each beat— both increase to accommodate this need. Regular exercise can increase a healthy person's HR to 150 bpm and SV significantly, resulting in increased CO—up to 4-5 times the resting rate. Pregnancy imposes similar demands on the cardiovascular system, leading to such an increase in CO.
It's interesting to note that the body's adaptations to exercise mirror some of the physiologic changes during pregnancy. For example, the pulse and blood pressure moderately rise during pregnancy, similar to the changes seen during physical exertion. However, during pregnancy, the rise in CO is not only due to an increased HR but also because of the increased SV to accommodate the expanded blood volume and fetal needs.