Final answer:
The nurse should instruct Ashley to push during contractions only, as this helps move the baby through the birth canal in synchronization with the body's natural labor process.
Step-by-step explanation:
During the second stage of labor, when Ashley feels rectal pressure and an urge to push, the RN should advise Jennie to push during contractions only. This is because effective labor pushing is synchronized with the body's natural contractions to help move the baby through the birth canal. Holding the breath for short periods while pushing can help, but continuous exertion can be exhausting and is not recommended. It's important for Ashley to conserve energy for when contractions occur and the body is naturally working to deliver the baby.