Final answer:
The nurse should teach the woman to come in to the birthing unit when contractions are 3 to 5 minutes apart.
Step-by-step explanation:
In a woman's birthing plan, the nurse should teach her to come in to the birthing unit when her contractions are 3 to 5 minutes apart. During the first stage of labor, the cervix dilates and effaces, and contractions become more frequent and intense. When contractions are consistently 3 to 5 minutes apart, it indicates that the woman is in active labor and should go to the birthing unit.