How is heart rate affected by pregnancy?

• A. Increases 10 to 20 beats per minute above baseline
• B. Decreases 10 to 20 bpm
• C. No change
• D. Increases 40-60 bpm

Answer: (A)

During pregnancy the heart must support a larger blood volume and higher metabolic demands, so the heart rate rises modestly to keep cardiac output adequate. Blood volume expands about 40–50%, and while systemic vascular resistance falls from progesterone-driven vasodilation, the need to perfuse both mother and placenta pushes the heart to beat a bit faster. The typical result is about a 10–20 beats per minute increase above the pre-pregnancy baseline, especially in the second trimester. This modest rise is normal and contrasts with the other patterns: a decrease would not meet the increased demand, no change would ignore the expanded blood volume, and a 40–60 bpm jump is larger than what is usually expected and could signal an abnormal condition.