What is the most common cause of sustained tachycardia in a term fetus?

Sustained tachycardia in a term fetus is most commonly associated with maternal or fetal infection. In this context, the presence of an infection can lead to systemic changes in both the mother and the fetus, causing an increase in heart rate. When the fetal heart rate is elevated, it often indicates that the fetus is responding to the maternal condition, which can include fever or inflammatory responses linked to infections.

Maternal or fetal infections can provoke a variety of reactions, including changes in blood flow, oxygenation, and metabolic demands, all of which can contribute to an increase in fetal heart rate. For instance, infections such as chorioamnionitis can directly impact the fetal environment and lead to a compensatory increased heart rate in an effort to maintain adequate perfusion and oxygenation despite the stressors present.

While other factors such as hypoxia due to delivery complications or maternal stress can contribute to variations in fetal heart rate, they are not as commonly identified as the primary cause of sustained tachycardia compared to infections. Genetic disorders are also less likely to cause immediate tachycardic responses in a term fetus. Recognizing the relationship between infections and fetal heart rate changes is crucial for timely intervention and management in clinical settings.