Which of the following cardiovascular changes of normal pregnancy is CORRECTLY matched with its physiological basis?

• A Decreased heart rate — progesterone-mediated vagal stimulation
• B Decreased blood pressure — due to fall in cardiac output overwhelms the increase in blood volume
• C Increased blood pressure in second trimester — due to placental angiotensin production
• D Increased cardiac output by 40–50% — due to increased stroke volume early, followed by increased heart rate; both contribute ✓

Explanation

Cardiac output increases by 40–50% during pregnancy. In the first trimester, the rise is primarily due to increased stroke volume (from expanded blood volume and reduced afterload). In the second trimester, heart rate also rises (10–15 bpm), contributing significantly. By term both stroke volume and heart rate are elevated. Blood pressure actually falls in the second trimester (due to progesterone-mediated systemic vasodilation and reduced peripheral resistance) and rises toward normal at term. The overall BP change is a decrease/normalization, not an increase. Progesterone causes vasodilation, not vagal stimulation.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.