During a prenatal assessment, what vital sign would suggest immediate intervention in a woman on magnesium sulfate?

In the context of a woman receiving magnesium sulfate, a respiratory rate of 12 breaths per minute indicates a potential respiratory depression, which is a significant concern. Magnesium sulfate is known to have a depressive effect on the central nervous system, and if respiratory rate decreases to 12 or below, it can suggest inadequate ventilation and an increased risk for respiratory failure. Interventions are necessary at this stage to ensure proper oxygenation and respiratory function.

While other vital signs may show alterations, they do not indicate an immediate risk of severe complications. A temperature of 100°F can be a common finding and may not require urgent intervention unless there are additional symptoms of infection. A heart rate of 92 beats per minute is generally within acceptable limits for a pregnant woman and does not signal immediate concern. Similarly, a blood pressure of 140/90 mm Hg, although higher than the ideal range, is not uncommon during pregnancy and does not typically necessitate immediate intervention unless it shows significant changes or symptoms of hypertension. Therefore, the respiratory rate is the most critical sign in this scenario, warranting immediate intervention.