What is the primary cause of fetal tachycardia?

Fetal tachycardia, characterized by a fetal heart rate greater than 160 beats per minute, can have multiple etiologies; however, maternal infection is recognized as a primary and common cause. When an infection occurs in the mother, it can lead to systemic inflammation and an increase in maternal temperature, which often results in an elevated fetal heart rate. This response is due to the fetal heart countering the maternal febrile state, reflecting the fetus's physiological response to stressors.

Evaluating the other options provides additional context. While placental abruption, fetal anemia, and maternal dehydration can contribute to changes in fetal heart rate, they are not typically the most common or direct causes of fetal tachycardia overall. Placental abruption can cause fetal distress, but its occurrence is more strongly associated with variable decelerations rather than consistent tachycardia. Fetal anemia, typically resulting from conditions such as Rh incompatibility or significant maternal blood loss, can cause bradycardia rather than tachycardia due to reduced circulating blood volume. Maternal dehydration may impact fetal heart rate as well, often leading to a response that can vary widely but is not as directly correlated with sustained tachycardia as an active maternal infection