Those new guidelines were issued today by an Institute of Medicine (IOM) committee of doctors, nutrition experts, and public health researchers.
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.
New Pregnancy Weight Guidelines
Here are the guidelines for pregnancy weight gain, based on a woman's BMI (body mass index) before becoming pregnant with one baby:
- Underweight: Gain 28-40 pounds
- Normal weight: Gain 25-35 pounds
- Overweight: Gain 15-25 pounds
- Obese: Gain 11-20 pounds
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."
During pregnancy, "women need to gain weight, but they don't need to gain an unlimited amount of weight. It is really hard to lose it afterward," Rasmussen says.
Linda Barbour, MD, MSPH, a professor of medicine and obstetrics-gynecology at the University of Colorado at Denver, disagrees with the idea that all women need to gain weight during pregnancy.
Barbour says she is "disappointed" that the IOM's new guidelines don't reflect recent data that suggest not gaining any weight during pregnancy may be OK for obese women, particularly those who are severely obese.
"There's been a lot of data suggesting that obese women really don't have to gain any weight to have a baby that is normally grown," Barbour says.
Eating for Two?
Talking with patients about weight and pregnancy can be difficult, says Melissa Goist, MD, clinical assistant professor in the obstetrics-gynecology department of the Ohio State University Medical Center.
Goist says many people aren't aware that there are limits on healthy weight gain during pregnancy.
"I think people still feel like pregnancy is fair game," Goist says. "You only need 300 extra calories per day to actually maintain a pregnancy."
So if you think eating for two means doubling your calories, forget it.
"If you think about the normal diet of maybe 1,800-2,000 calories, depending on the size of the person, 300 extra calories is a sixth of that. So that's barely like eating anything," Goist says.
The IOM's new guidelines call for women to be offered preconception counseling that includes their weight, diet, and physical activity.
Most women don't get preconception counseling, Rasmussen says.
Goist agrees. Only about 10% of her patients ask how they can get healthier before pregnancy, and "probably less than 1% of those patients are women who are obese with concerns that maybe they need to lose weight prior to getting pregnant," Goist says.
"It would be huge" for all women considering pregnancy to get preconception counseling, Goist says. "I think that if all patients thought that's what they were supposed to do, potentially we would have more patients doing it."
Delaying Pregnancy to Lose Weight
Rasmussen acknowledges debate among obstetricians about whether overweight or obese women should consider contraception until reaching a healthy weight.
"But certainly, we would like to see as many women as possible conceive at a healthy weight that will reduce their general obstetric risk," Rasmussen says.
Goist says most of her patients don't like the idea of delaying pregnancy so they can lose extra pounds.
"When you're telling a patient, 'I want you to take a break for six months and try to lose 20 pounds,' they think that you might be the devil incarnate," Goist says.
But Goist says most of her overweight patients already know that they need to lose some weight, and that it helps to talk with them about taking care of their own health so they can be there for their kids as they grow up.
"Your mentality changes when you're a mom, because you have other people to take care of," she says.
An avid exerciser and mother of two, Goist says she didn't have trouble gaining the right amount of weight during her pregnancies, in part because she wanted to be a role model to her patients. Even so, she says "it was harder to lose the weight the second time vs. the first time."
Read more about the new pregnancy weight guidelines on WebMD's news blog.