Final answer:
If a pregnant patient's test results are negative for glucose but positive for acetone, the nurse should assess the maternal hydration status.
Step-by-step explanation:
If a pregnant patient's test results are negative for glucose but positive for acetone, the nurse should assess the maternal hydration status. Acetone is formed in the human body as a by-product of lipid metabolism, and in certain disease states, such as uncontrolled diabetes mellitus, its concentration may rise to higher levels. In severe cases, the odor of acetone can be noted on the breath, indicating ketosis. Ensuring adequate hydration is crucial to support the mother's well-being and prevent complications.