Which statement best describes the change in infant pulse rate during the first year?

Which statement best describes the change in infant pulse rate during the first year?

• A. Pulse rate increases from 100 to 140.
• B. Pulse rate decreases from 120-140 to about 100.
• C. Pulse rate stays constant at 120-140.
• D. Pulse rate increases to 180.

Answer: (B)

Infants show a high resting pulse rate that gradually slows as they grow. At birth the heart works hard to meet metabolic demands, and the autonomic nervous system is still maturing, so the pulse is quite fast. As the infant’s body size increases, stroke volume rises and parasympathetic control becomes more established, allowing the heart to meet the body's needs with fewer beats per minute. The typical pattern is a decline from about 120–140 beats per minute in infancy toward around 100 beats per minute by the end of the first year. Rates that rise to 180 at rest or stay consistently high, or that remain around 120–140 without decreasing, don’t fit the normal developmental trajectory.

Infants show a high resting pulse rate that gradually slows as they grow. At birth the heart works hard to meet metabolic demands, and the autonomic nervous system is still maturing, so the pulse is quite fast. As the infant’s body size increases, stroke volume rises and parasympathetic control becomes more established, allowing the heart to meet the body's needs with fewer beats per minute. The typical pattern is a decline from about 120–140 beats per minute in infancy toward around 100 beats per minute by the end of the first year. Rates that rise to 180 at rest or stay consistently high, or that remain around 120–140 without decreasing, don’t fit the normal developmental trajectory.