My pre-pregnancy weight was 82 pounds. I've weighed that for about ten years, and my caloric intake has always been around 1,300. I've gained a total of only 3 pounds in the first 15 weeks of my pregnancy. It's important for you to discuss with your doctor what he or she thinks is an appropriate weight gain for you. The general rule is 25 to 35 pounds for those with a normal body weight pre-pregnancy.
Underweight women can gain slightly more.
In the first trimester , a recommended amount of weight gain is 3 to 4 pounds. That changes to about one pound a week during the second trimester. You might want to consider eating at least six small meals each day so you can obtain adequate calories. If you try to get 400 calories at each small meal, this will provide 2,400 calories per day, which would be a reasonable goal. If you get full quickly, you might try to drink your calories through milkshakes and juices.