How much weight should I gain in my first trimester?

I never gained much, if any, weight during the first half of each of my pregnancies. If you're at a normal weight you're supposed to gain no more than 1/2 a pound a week during the first trimester, and 1 pound per week during the third trimester. Your weight gain should be 25-30 pounds for the entire pregnancy. If you are overweight you should gain 15-20 pounds, if you are underweight you should gain 35-40 pounds.