You should see a dietitian if you are diagnosed with diabetes. A dietitian will explain you how many calories you need each day. Then she'll teach you how to determine portion sizes and how to balance your meals with just the right amounts of protein, carbohydrates, and fat. She'll also assess your current eating habits to make sure you're getting enough vitamins and minerals for you as well as your growing fetus.
I can tell you some thumb rules of diet:
Eat a variety of foods, distributing calories and carbohydrates evenly throughout the day. Make sure both your meals and your snacks are balanced.
Don't skip meals. Be consistent about when you eat them and the amount of food you eat at each one. Stable Blood sugar level will ensure good health of your growing baby.
Include high-fiber foods, such as fresh fruits and vegetables, whole grain breads and cereals, and dried peas, beans, and legumes.
avoid beverages that contain simple sugars such as soda, fruit juice, flavored teas, and most desserts — or avoid them altogether. These foods can quickly elevate your blood sugar. Ask your healthcare practitioner about using foods sweetened with an artificial sweetener if you need a sweet fix.
Milk is high in lactose, a simple sugar, so if you drink more than two or three glasses a day, you may need to limit the amount you drink and find an alternative source of calcium.
Fast food are empty calories, and bad carbs, now you need to have a break on them.