It's the first time the IOM has issued pregnancy weight guidelines since 1990, and in the past 19 years, America's obesity boom has only grown.
But the new guidelines aren't just for women who are overweight before pregnancy. They're for women of all sizes, starting with a prepregnancy checkup that addresses weight, diet, and exercise -- and a discussion about using contraception, too, until overweight or obese women reach a healthy weight.
During pregnancy, many women gain "substantially more than we would like," IOM committee chairwoman Kathleen Rasmussen, ScD, PhD, tells WebMD.
"It is important for women to gain within [the new guidelines] and if possible, it's important for women to begin pregnancy at a good weight," says Rasmussen, who is also a Cornell University nutrition professor.
And here are the guidelines for weight gain during pregnancy with twins, based on the mother's prepregnancy BMI:
Normal weight: Gain 37-54 pounds
Overweight: Gain 31-50 pounds
Obese: Gain 25-42 pounds
Underweight: No weight gain guidelines are available because of insufficient data.
"For women to achieve these goals, they are going to need individualized attention before, during, and after pregnancy," with support from their doctors, families, and communities, Rasmussen says.
The IOM's new pregnancy weight gain guidelines are similar to its 1990 guidelines, except now there is an upper limit on how much weight obese women should gain while pregnant.
"The fact that the numbers are the same suggests that they have withstood the scrutiny that they've received in the last 19 years. So women can have confidence in these targets," Rasmussen says. She says that although the 1990 guidelines focused on infant health, the new guidelines also consider the mother's health.
Overdoing Pregnancy Weight Gain
Gaining too much weight during pregnancy may be risky for the mother and the baby.
"The risk for the baby is being born too large, which can result in birth injury for the baby or may result in a cesarean section for the mother," Rasmussen says. "The risks for the mother of gaining beyond the guidelines are risk for cesarean section or risk for excessive weight retention postpartum."
The new guidelines don't advise any women to lose weight while pregnant.
"Pregnancy isn't a time when you should be losing weight," Rasmussen says. "Some women do, but the targets that we've set, on the basis of the data that we have, don't have anybody losing weight while they're pregnant."