Final answer:
When a client comes to the hospital in labor and their membranes rupture, the nurse should first assess the fetal heart rate.
Step-by-step explanation:
When a client comes to the hospital in labor and their membranes rupture, the first action the nurse should take is to assess the fetal heart rate. By checking the fetal heart rate, the nurse can determine if the baby is experiencing any distress or if any other immediate concerns need to be addressed. This information will help guide further interventions and decision-making during the labor process.