What is a common cause of fetal heart rate bradycardia?

Prolonged cord compression is a significant cause of fetal heart rate bradycardia because it can lead to a reduction in blood flow and oxygen to the fetus. This compression typically occurs during contractions, particularly if the umbilical cord becomes wrapped around the fetus or is compressed between the fetus and the maternal pelvis. When the cord is compressed, it can cause a decrease in fetal heart rate due to the interruption of oxygen delivery, triggering a reflex that results in bradycardia.

In contrast, maternal dehydration, excessive fetal movement, and the use of narcotics during labor can have different effects on fetal heart rate. Maternal dehydration may contribute to other complications but is not a direct cause of bradycardia. Excessive fetal movement can sometimes be associated with variable decelerations but is not typically linked with sustained bradycardia. The use of narcotics can lead to decreased fetal heart rates, but this typically results in alterations in variability rather than outright bradycardia. Therefore, prolonged cord compression stands out as a more direct and common cause of fetal heart rate bradycardia.