If you're overweight when you get pregnant, you face these increased risks: high blood pressure, gestational diabetes, and preeclampsia, which means a greater chance of a premature birth. But even if you weigh too much when you start out, there are healthy ways to gain the right amount:

Don't diet. "If you restrict your caloric or carbohydrate intake, your baby won't get what he needs to grow," says Toya Ellis, M.D., an ob-gyn at the Kaiser Permanente Health Plan.

Don't eat for two. Ignore everyone who urges you to eat whatever you want because you're pregnant. If you're overweight, you need less than 300 extra calories a day  -- the equivalent of a nonfat yogurt with a sprinkling of granola.

Do exercise  -- but don't go overboard. Getting active is a great way to combat extra pounds. But if you've always been a bit of a couch potato, take it easy; starting something strenuous now can decrease blood flow to your baby. Your best bet: walking every day.

Do start good habits now. We all want the best for our babies, so let that feeling steer you away from junk food and toward healthier choices. The next time you crave a shake, go for a low-fat smoothie; substitute pretzels for potato chips. The habits you adopt now are likely to carry over postpartum.

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