The US Institute of Medicine and the National Research Council has recommended that obese women limit their weight gain to 11 to 20 pounds during pregnancy.
The new guidelines update recommendations the Institute of Medicine made in 1990 and reflect changing U.S. demographics, particularly the surge in the number of Americans who are overweight or obese.
Healthy American women at a normal weight for their height (BMI of 18.5 to 24.9) should gain 25 to 35 pounds during pregnancy, the new guidelines state. Underweight women (BMI less than 18.5) should gain more, 28 to 40 pounds, and overweight women (BMI of 25 to 29.9) should gain less, 15 to 25 pounds. These ranges match the 1990 guidelines, but the report also specifies a new range for obese women (BMI greater than 30) that limits their gain to 11 to 20 pounds.
In a report released Thrusday, the Institute said that entering pregnancy with a normal body mass index (BMI) as well as gaining within the recommended levels during gestation were the best ways to minimize risks.
"A growing amount of scientific evidence indicates that how much weight women gain during pregnancy and their starting weight at conception can affect their health and that of their babies," it said and called for increased diet and exercise counseling and programs to help women attain a normal BMI.
"This report gives women and their health care providers an evidence-based answer to the question of how much weight women should gain during pregnancy," said Kathleen M. Rasmussen, professor of nutrition, division of nutritional sciences, Cornell University, Ithaca, N.Y., and chair of the committee that wrote the report. "We call on health professionals to adopt these guidelines and help women follow them so that mothers and their children will have the best health outcomes possible."
Expectant mothers and their care providers need to balance the benefits of pregnancy weight gain for the fetus with the risks of too much or too little increase, which can result in consequences for both mothers and children. For mothers, the ramifications of excess weight gain include increased chances of retaining extra pounds after birth or needing a Caesarean section; for children the risks include being born preterm or larger than normal with extra fat. Each of these consequences increases the chances for subsequent health problems -- such as heart disease and diabetes in the case of extra weight, and impaired development in the case of premature birth. At the same time, adding too few pounds during pregnancy increases risks for stunted fetal growth and preterm delivery.
The report focuses on weight changes during pregnancy, but it also notes that women's weight at conception affects infants and mothers, too. Nearly two-thirds of U.S. women of childbearing age are overweight or obese. To minimize the risks, women should aim to conceive while at a normal BMI and gain within the guidelines during pregnancy, the committee concluded.
Helping women achieve these goals will require health care providers to increase the counseling they give their patients on weight, diet, and exercise. This counseling should occur not just during pregnancy, but well before women plan to conceive, given that many should lose weight to begin pregnancy closer to or at a normal BMI. Women's doctors should record their patients' weight, height, and BMI as a routine practice prior to conception, throughout pregnancy, and in the post-partum period. Prenatal care providers and expectant mothers should work together to set pregnancy weight gain goals based on the guidelines and other factors relevant to each patient's individual needs.
Guidelines do no good if women do not know about them and care providers do not follow and promote them. Studies published after the 1990 guidelines were released found that a high proportion of women were either given no advice on how much weight to gain or were advised to gain outside of their recommended range. The committee called on medical professional societies, federal health agencies, and other influential groups to adopt the new guidelines and help educate women on their importance for achieving healthy outcomes for their children and themselves.
The guidelines are essentially intended for American women. They may be applicable to women in other developed countries, but they are not intended for use in areas of the world where women are substantially shorter or thinner than American women or where adequate obstetric services are not available, the Institute cautioned.
The study was sponsored jointly by the government agencies including Department of Health and Human Services' Health Resources Services Administration, Centers for Disease Control and Prevention and National Institutes of Health and some nonprofits.