May 28 (HealthDay News) -- Obese moms-to-be should limit their weight gain during pregnancy to between 11 and 20 pounds to safeguard their health and that of their baby, according to newly updated expert guidelines.
That level of gestational weight gain is about half whats recommended for normal-weight pregnant women and reflects the concern over the rising number of obese expectant mothers in the United States.
The new guidelines -- the first since 1990 -- were issued jointly May 28 by the Institute of Medicine and the National Research Council.
"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," explained Dr. Patrick M. Catalano, chairman of obstetrics and gynecology at Case Western Reserve University and 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," Catalano said.
Doctors 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 a rise in risk for preterm birth or being larger than normal at delivery, with extra fat, Catalano noted. Babies born large can suffer stuck shoulders and broken collar bones, 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 noted, women who are underweight during their pregnancy raise their babies' odds for stunted fetal growth and preterm delivery.
So, 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 recommended, 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 doctors 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 November in Obstetrics & Gynecology, nearly one in five pregnant American women now surpass recommended levels of weight gain during their pregnancies.
So, following the new guidelines "can be beneficial to both you and the baby," Catalano said. "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."
Dr. Michael Katz, senior vice president for research and global programs 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," Katz said. "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, Katz noted. Being underweight is also a problem, "but obesity is by far the most prevalent and most serious problem," he said.
SOURCES: Patrick M. Catalano, M.D., chairman, Department of Obstetrics and Gynecology, Case Western Reserve University, Cleveland; Michael Katz, M.D., senior vice president for research and global programs, March of Dimes, White Plains, N.Y.; May 28, 2009, Institute of Medicine and National Research Council report, Weight Gain During Pregnancy: Reexamining the Guidelines