A 30-year-old woman (G2P0) is experiencing preterm labor at 26-weeks gestation.

Comprehensive and Detailed Explanation From NCC-Aligned Sources:

This tracing shows:

Baseline ~170–175 bpm → fetal tachycardia

Minimal variability

No contractions of significance

Maternal treatment with magnesium sulfate, which typically decreases baseline and variability—not increase it

NCC and AWHONN physiology guidelines emphasize that fetal tachycardia is most commonly associated with maternal infection, including chorioamnionitis, especially in preterm labor.

Magnesium sulfate does not cause tachycardia; it generally causes:

↓ baseline

↓ variability

Thus, fetal tachycardia + minimal variability in a preterm patient strongly suggests maternal infection, requiring evaluation for chorioamnionitis.

Why the wrong answers are incorrect:

A. Acetaminophen → used after confirming fever, not before evaluating the cause.

B. Discontinuing magnesium → magnesium sulfate does not cause tachycardia; discontinuing it removes fetal neuroprotection.