## **Core Concept**
The question pertains to the characteristics of uterine contractions, specifically in the context of a spastic lower uterine segment during labor. Uterine contractions are crucial for the progression of labor, and abnormalities in these contractions, such as spasticity in the lower segment, can lead to obstructed labor.

## **Why the Correct Answer is Right**
A spastic lower uterine segment is associated with abnormal uterine contractions that can impede the normal process of labor. Features of such contractions may include increased resting tone, uncoordinated contractions, and failure of the lower segment to relax and dilate. The correct answer choice highlights a feature that does not align with these characteristics.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Increased resting tone is a feature of abnormal uterine activity, including spastic lower segment. This condition can lead to inadequate relaxation between contractions, potentially causing fetal distress and obstructed labor.
- **Option B:** Incoordinate contractions are also characteristic of abnormal uterine activity. These contractions are not synchronized across the uterus, which can lead to inefficient labor progress.
- **Option D:** High amplitude contractions can be seen in the context of spastic lower segment, contributing to the obstruction of labor.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that a spastic lower uterine segment can lead to significant complications, including uterine rupture. Identifying and managing abnormal uterine contractions early in labor is crucial to prevent such outcomes.

## **Correct Answer:** D. Decreased resting tone between contractions.