Final answer:
The cessation of contractions several hours after the infusion of magnesium sulfate suggests that the drug is effectively working as a tocolytic therapy to prevent premature labor, and the nurse should monitor the patient's reflexes for signs of toxicity.
Step-by-step explanation:
The best analysis of the data indicating that contractions have ceased several hours after a magnesium sulfate infusion is that the drug is having a therapeutic effect. Magnesium sulfate is often prescribed as a tocolytic therapy to inhibit uterine contractions and prevent premature labor. When contractions cease, this typically means that the medication is effectively helping to relax the uterus. However, because magnesium sulfate can have side effects such as affecting deep tendon reflexes, it would be prudent for the nurse to regularly assess the patient's deep tendon reflexes to monitor for signs of magnesium toxicity.