Uterine resting tone is the pressure within the uterus:

Uterine resting tone refers to the baseline pressure within the uterus when it is not actively contracting. It is an important parameter in fetal heart monitoring, as it helps clinicians assess uterine activity and overall uterine health. The resting tone reflects the degree of tension or relaxation in the smooth muscle of the uterus and is measured when there is no contraction occurring.

When evaluating the answers provided, the correct choice emphasizes the state of the uterus at a time when all contractions have subsided, allowing for a clear measurement of the baseline pressure. In contrast, the other options either refer to periods when the uterus is active during contraction or when cervical changes like dilation are occurring, which would not be useful in determining the resting tone. Therefore, recognizing that uterine resting tone is specifically defined as the pressure present between contractions reinforces the importance of understanding normal uterine physiology during the monitoring process.