What condition may fetal tachycardia (sustained 170s-180s) commonly indicate?

Fetal tachycardia, defined as a sustained heart rate above 160 beats per minute, can be an important indicator of underlying maternal or fetal conditions. Among the options provided, maternal infection is the most likely condition associated with sustained fetal tachycardia in the range of 170s to 180s.

When a mother has an infection, the body's response can lead to a fever and increased metabolic demand. This heightened state can directly affect the fetus, often resulting in tachycardia as the fetal body responds to the mother's altered physiological state. Infections such as chorioamnionitis—an infection of the membranes surrounding the fetus—are particularly associated with fetal tachycardia and can pose serious risks to both mother and baby.

In contrast, while maternal diabetes, dehydration, and hypertension can influence fetal heart rate, they do not commonly lead to sustained fetal tachycardia in the same way that an infection typically does. Maternal diabetes is more often associated with a range of metabolic abnormalities, dehydration could affect the fetal condition but is not as directly linked to an elevated heart rate, and hypertension may commonly result in variations in fetal heart tracings but is less frequently directly correlated with sustained tachycardia.

Understanding these