Final answer:
The most important health history information to communicate before an oral glucose tolerance test is the patient's use of oral contraceptives, as it can impact the results.
Step-by-step explanation:
When preparing a female patient for an oral glucose tolerance test (GTT), several aspects of her health history are important. However, the most relevant information to communicate to the health care provider includes whether the patient uses oral contraceptives. This is due to the fact that oral contraceptives can affect carbohydrate metabolism and potentially impact the results of the glucose tolerance test. While the patient's exercise habits, pregnancy history, and family history of diabetes are relevant to her overall health, the use of oral contraceptives could directly influence the outcome of the GTT and the interpretation of whether or not the patient has a carbohydrate metabolism disorder such as diabetes mellitus.