Eating for two? New guidelines are setting how much weight women should gain during pregnancy — not too much if women already are overweight or obese when they conceive.

The Institute of Medicine issued guidelines Thursday that aren't too different from what obstetricians already recommend, but more than half of pregnant women don't follow them. Adding to that concern, women who become pregnant today tend to be heavier, older and have more conditions such as diabetes than just a decade ago — issues that make extra pounds riskier.

The recommendations: A normal-weight woman, as measured by the BMI or body mass index, should gain between 25 and 35 pounds. An overweight woman should gain 15 to 25. And for the first time there's a recommendation for obese women: 11 to 20 pounds.