**Core Concept**
Fetal distress during delivery can be caused by various factors, including umbilical cord compression. This compression can lead to a decrease in blood flow and oxygenation, resulting in fetal deceleration. Fetal deceleration is a critical indicator of fetal distress and can have serious consequences if not addressed promptly.

**Why the Correct Answer is Right**
Cord compression causes deceleration by impeding the normal flow of blood and oxygen to the fetus. This compression can occur due to various reasons, including prolapse, knots, or entanglement of the umbilical cord. The resultant decrease in blood flow triggers a response in the fetus's autonomic nervous system, leading to a decrease in heart rate, which is known as deceleration. This deceleration is a sign of fetal distress and requires immediate medical attention.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cord compression primarily affects blood flow and oxygenation, not the heart rate itself. While heart rate changes can occur, they are a secondary effect of the primary issue of cord compression.
**Option B:** This option is incorrect because cord compression does not directly cause acceleration. Acceleration is typically seen in response to fetal hypoxia, but it is not a direct consequence of cord compression.
**Option C:** This option is incorrect because cord compression can cause a variety of fetal heart rate patterns, including deceleration, but it is not the only possible outcome.

**Clinical Pearl / High-Yield Fact**
During delivery, it is essential to monitor fetal heart rate patterns closely, as changes in these patterns can indicate fetal distress. Cord compression is a common cause of fetal deceleration, and prompt recognition and intervention are critical to prevent long-term consequences for the fetus.

**Correct Answer:** D.