A nurse is preparing to administer magnesium sulfate IV to a client who is experiencing preterm labor. Which of the following is the priority nursing assessment for this client?

A. Fetal heart rate (FHR): While FHR monitoring is important, the priority is assessing the mother's respiratory status due to the risk of magnesium toxicity, which can lead to respiratory depression. B. Bowel sounds: Magnesium sulfate can cause decreased gastrointestinal motility, but bowel sounds are not the immediate priority. The nurse should monitor for paralytic ileus, but respiratory function takes precedence. C. Respiratory rate: Magnesium sulfate is a central nervous system (CNS) depressant that can cause respiratory depression if levels become too high. A respiratory rate below 12 breaths per minute is a sign of magnesium toxicity, requiring immediate intervention (e.g., stopping the infusion and administering calcium gluconate). D. Temperature: Temperature is not directly affected by magnesium sulfate administration, making it a lower-priority assessment compared to respiratory rate.