Pregnant women were once urged to eat, eat, eat — good advice when food was scarce. But in the U.S., nearly two-thirds of women of childbearing age are overweight or obese. Too much weight gain during pregnancy can lead to hypertension and diabetes for the mother and makes the kids 42% likelier to be obese beginning at age 9. The Institute of Medicine thus issued new weight guidelines for mothers this year. Women are grouped according to body mass index (BMI), a ratio of height to weight. Those with a healthy BMI of 18.5 to 24.9 are advised to gain 25 to 35 lb. during pregnancy. Overweight women, with a BMI of 25 to 29.9, should gain up to 25 lb. Obese women, with a BMI of 30 or more, should gain just 11 to 20 lb. Underweight women, with a BMI below 18.5, should gain up to 40 lb. The guidelines apply only to women in the U.S., not to those in places where moms-to-be are shorter or thinner or have inadequate prenatal care.