Which of the following best describes a reactive nonstress test?

• A. Baseline 110-160/min with moderate variability and 2 or more accelerations in 20 minutes.
• B. Baseline 140-170/min with no accelerations in 40 minutes.
• C. Baseline 90-100/min with marked variability and no accelerations.
• D. Baseline 120/min with low variability and 1 acceleration in 20 minutes.

Answer: (A)

A reactive nonstress test means the fetus is showing heart-rate accelerations in response to movement, suggesting good oxygenation and CNS function. For a test to be reactive, the tracing must have a normal baseline of about 110–160 bpm, moderate variability, and at least two accelerations of at least 15 bpm above baseline lasting 15 seconds or more within a 20-minute period.

The option describing a baseline of 110–160, with moderate variability, and two or more accelerations in 20 minutes matches this pattern, making it the correct description of a reactive NST.

Why the others don’t fit: a tracing with no accelerations in a longer observation period is nonreactive; a fetal baseline of 90–100 bpm with no accelerations is bradycardic and nonreactive; and a tracing with only one acceleration in 20 minutes and low variability does not meet the two-acceleration requirement for reactivity.