During a woman's 38-week prenatal visit, the fetal heart rate is 180 beats per minute. What might the nurse suspect as the most likely cause of this tachycardia?

• A. Maternal infection
• B. Gestational hypertension
• C. Gestational diabetes mellitus
• D. Consumption of recent high-sugar snack

Answer: (A)

Fetal tachycardia—when the heart rate is markedly elevated above the normal range (typically over 160 bpm)—is often a sign of fetal stress or illness. In the late third trimester, the most likely cause of a sustained high fetal heart rate such as 180 bpm is maternal infection, especially if fever is present. Infections like chorioamnionitis can raise the fetus’s metabolic demand and trigger increased heart rate as part of the inflammatory response.

Gestational hypertension and gestational diabetes affect the pregnancy in other ways, mainly through placental perfusion and metabolic changes over time, and they don’t typically cause a sudden, isolated tachycardia like this. A recent high-sugar snack wouldn’t produce a persistent fetal tachycardia either.

So the finding points toward maternal infection as the most likely cause, and it calls for prompt assessment and monitoring of both mother and fetus to identify and treat any infection.