In the meanwhile provide advice about medical nutrition and exercise

Nutrition therapy improves glycemic control for both GDM and overt DM pregnants. Most GDM cases are effectively treated with medical nutrition combined to exercise, and pharmacological therapy is needed in less than 20% of pregnant diagnosed with GDM. So:

R 4.1, R 2.3b Recommend medical nutrition therapy for all pregnant women diagnosed with overt DM or GDM to help achieve and maintain desired glycemic control while providing essential nutritional requirements. (1++)

R 2.3b Recommend initial treatment of GDM should consist of medical nutrition and daily moderate exercise for 30 minutes or more. (1+++) 

R 4.2b In cases when the pregnant is overweight or obese, suggest reduction of calorie intake by one third while maintaining minimum intake of 1600-1800kcal. (2++) 

R 4.3 Limit carbohydrate intake to 35-45% of total calories distributed to 3 small-to moderate-sized meals and 2-4 snacks including an evening snack. (2++)