In the first trimester, most people don't need to gain much weight. This is good news if you're struggling with morning sickness.
If you start out at a healthy weight, you need to gain only about 1 to 4 pounds (0.5 to 1.8 kilograms) in the first few months of pregnancy. You can do this by eating a healthy diet — no extra calories are necessary.
Steady weight gain is more important in the second and third trimesters — especially if you start out at a healthy weight or you're underweight. According to the guidelines, you'll gain about 1 pound (0.5 kilogram) a week until delivery. An extra 300 calories a day — half a sandwich and a glass of skim milk — might be enough to help you meet this goal. For people who are overweight or obese, the guidelines translate to a weight gain of about 1/2 pound (0.2 kilogram) a week in the second and third trimesters. Try adding a glass of low-fat milk or an ounce of cheese and a serving of fresh fruit to your diet.