What can cause transient decelerations in the fetal heart rate?

Transient decelerations in the fetal heart rate are often caused by cord compression, particularly during uterine contractions. When the umbilical cord is compressed, it can restrict blood flow and oxygen delivery to the fetus, leading to a temporary decrease in heart rate. This is typically observed as a variable deceleration on fetal heart monitoring and can occur in conjunction with contractions due to the increased pressure on the cord.

Other factors such as fetal movement, maternal sleep, and chronic health conditions in the mother do not typically cause transient decelerations. While fetal movement is generally associated with changes in heart rate, it usually leads to accelerations rather than decelerations. Maternal sleep can result in a lower baseline fetal heart rate but does not directly cause transient decelerations. Chronic health conditions in the mother might have long-term effects on fetal well-being but are not known to be a direct cause of transient decelerations. Thus, the role of cord compression during contractions is crucial in understanding why it is the correct answer.