Final answer:
The recommended testing for pre-pregnancy screening of diabetes mellitus (DM) in patients with gestational diabetes mellitus (GDM) includes the Glucose Tolerance Test (GTT) and further investigations if GTT is positive.
Step-by-step explanation:
The recommended testing for pre-pregnancy screening of diabetes mellitus (DM) in patients with gestational diabetes mellitus (GDM) includes the Glucose Tolerance Test (GTT) and further investigations if GTT is positive. The GTT is performed by measuring blood glucose levels in fasting condition, followed by an oral dose of glucose. Blood glucose levels are then measured at regular intervals to assess the individual's ability to tolerate glucose, which helps in diagnosing diabetes mellitus. If GTT is positive, additional tests like Insulin Tolerance Test (ITT) and Glucagon Tolerance Test (GuTT) can be done to determine the type of diabetes.