Obese moms-to-be should limit their weight gain to between 11 and 20 pounds during pregnancy to safeguard their health and that of their baby, say experts.
The new guidelines - the first since 1990 - were issued jointly by the Institute of Medicine (IOM) and the National Research Council.
The level of gestational weight gain is about half of what is recommended for normal-weight pregnant women and reflects the concern over the rising number of obese expectant mothers in the US.
"We looked at a balance of maternal outcomes related to weight gain in pregnancy and issues related to the outcome for the fetus and neonate," says Dr. Patrick M. Catalano, at Case Western Reserve University in Cleveland, Ohio, who is a member of the committee that wrote the new guidelines.
"There is good evidence that the amount of gestational weight gain for an obese woman can be related to the risk of needing a cesarean delivery and retention of weight gain after pregnancy, which puts the woman at further risk in future pregnancies," says Dr. Catalano.
Physicians typically define overweight as a body mass index (BMI) of between 25 and 30 and obesity as a BMI of 30 and above.
BMI is based on weight and height; for example, a 5-foot-6-inch tall woman weighing between 115 and 154 pounds would have a BMI in the normal range.
But children born to overweight or obese moms face an increased risk for preterm birth or being larger than normal at delivery, with extra fat, notes Dr. Catalano.
Large babies can suffer stuck shoulders and broken collar bones during birth, experts say, and are prone to overweight or obesity and type 2 diabetes later in life.
And an overly large newborn poses risks for the mother at delivery, including vaginal tearing, bleeding, and often the need for a cesarean section.
Infants born overweight also face higher odds for health problems such as heart disease and diabetes. Children born prematurely can suffer from impaired mental and physical development.
On the other end of the spectrum, the report's authors note, women who are underweight during their pregnancy raise their babies' odds for stunted fetal growth and preterm delivery.
According to the new guidelines, maintaining a normal body weight and gaining only the recommended amount of weight during pregnancy is the best way to lower risks to both mother and child.
Specifically, the guidelines urge that:
Normal-weight women - those with a BMI of 18.5 to 24.9 - should gain 25 to 35 pounds during pregnancy.
Underweight women - those with a BMI less than 18.5 - should gain 28 to 40 pounds during pregnancy.
Overweight women should gain 15 to 25 pounds.
Obese women should gain only 11 to 20 pounds.
The last recommendation marks a change from the 1990 guidelines, which recommended that obese mothers-to-be gain at least 15 pounds during pregnancy.
The report's authors were also concerned with the mother's weight at conception. Almost two-thirds of American women of childbearing age are overweight and almost one-third are obese, the report notes.
The committee recommends, therefore, that women try to reach a normal BMI before conception and then gain the appropriate amount of weight during their pregnancy.
The committee also recommends that physicians provide diet and exercise counseling to women before conception so that women can achieve a normal BMI before becoming pregnant.
In addition, prenatal care should focus on keeping weight gain within recommended guidelines.
Putting on excess pounds during pregnancy is becoming common: According to a study published in the journal Obstetrics & Gynecology, nearly one in five pregnant American women now surpass recommended levels of weight gain during their pregnancies.
"The closer to a normal weight that you can be before you get pregnant is to your advantage and also to your baby's advantage because we know that your pre-pregnancy weight is a very important variable for these outcomes as well as the weight gain in pregnancy," says Dr. Catalano.
Dr. Michael Katz, at the March of Dimes, a sponsor of the report, was dubious about the impact of the new guidelines long term.
"Pregnant women are very concerned about the outcome so they respond to recommendations, but they don't last very long," says Dr. Katz. "Obesity and overweight is a chronic situation. If a woman is overweight, she should adjust her weight first, then become pregnant. And one hopes, they would keep their weight in check subsequently, but that's unlikely."
Losing weight and keeping it off is a lifetime commitment, notes Dr. Katz. Being underweight is also a problem, "but obesity is by far the most prevalent and most serious problem," he says.
Always consult your physician for more information.
Obesity is a chronic disease affecting increasing numbers of children and adolescents as well as adults.
Obesity rates among children in the US have doubled since 1980 and have tripled for adolescents. About 17 percent of children aged two to 19 are considered overweight compared to over 66 percent of adults who are considered overweight or obese.
Earlier onset of type 2 diabetes, cardiovascular disease, and obesity-related depression in children and adolescents is being seen by healthcare professionals.
The longer a person is obese, the more significant obesity-related risk factors become. Given the chronic diseases and conditions associated with obesity and the fact that obesity is difficult to treat, prevention is extremely important.
A primary reason that prevention of obesity is so vital in children is because the likelihood of childhood obesity persisting into adulthood is thought to increase as the child ages.
Many of the strategies that produce successful weight loss and maintenance help prevent obesity. Improving eating habits and increasing physical activity play a vital role in preventing obesity.
Eat five to nine servings of fruits and vegetables daily. A vegetable serving is one cup of raw vegetables or one-half cup of cooked vegetables or vegetable juice. A fruit serving is one piece of small to medium fresh fruit, one-half cup of canned or fresh fruit or fruit juice, or one-fourth cup of dried fruit.
Choose whole grain foods such as brown rice and whole wheat bread. Avoid highly processed foods made with refined white sugar, flour, and saturated fat.
Weigh and measure food in order to be able to gain an understanding of portion sizes. For example, a 3-ounce serving of meat is the size of a deck of cards. Avoid supersized menu items.
Balance the food "checkbook." Taking in more calories than are expended for energy will result in weight gain. Regularly monitor weight.
Avoid foods that are high in "energy density," or that have a lot of calories in a small amount of food. For example, a large cheeseburger with a large order of fries may have almost 1,000 calories and 30 or more grams of fat. By ordering a grilled chicken sandwich or a plain hamburger and a small salad with low-fat dressing, you can avoid hundreds of calories and eliminate much of the fat intake.
For dessert, have fruit or a piece of angel food cake rather than the "death by chocolate" special or three pieces of home-made pie.
Remember that much may be achieved with proper choices in serving sizes.
Accumulate at least 30 minutes or more of moderate-intensity activity on most, or preferably all, days of the week. Examples of moderate intensity exercise are walking a 15-minute mile, or weeding and hoeing a garden.
Look for opportunities during the day to perform even ten or 15 minutes of some type of activity, such as walking around the block or up and down a few flights of stairs.
Always consult your physician for more information.
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