Eating a variety of foods that provide enough calories helps you and your baby gain the proper amount of weight. During the first three months of pregnancy, you do not need to change the number of calories you get from the foods you eat.
Normal-weight women need an extra 300 calories each day during the last six months of pregnancy. This totals about 1,900 to 2,500 calories per day. If you were underweight, overweight or obese before you became pregnant, or if you are pregnant with more than one baby, you may need a different number of calories. Talk to your doctor about how much weight you should gain and how many calories you need.
— Source: National Institutes of Health