June 2 (HealthDay News) -- In a study that reinforces recent changes in pregnancy weight gain recommendations, obese women who gained little or no weight while pregnant had better outcomes than obese women who gained more.
Just last week, experts at the U.S. Institute of Medicine and the National Research Council updated their gestational weight gain guidelines to urge that obese women gain only 11 to 20 pounds during pregnancy -- down from a minimum weight gain of 15 pounds that had been recommended in 1990.
In the new study, published in the June issue of the Journal of the National Medical Association, researchers divided 232 obese women, all with a body mass index greater than 30, into two groups. One group was given standard advice: to "eat to appetite." The other group was given nutritional counseling, told to keep a food diary and placed on a diet that limited calories to between 2,000 and 3,500 a day, depending on their pre-pregnancy weight.
By the end of the pregnancy, the average weight gain in the group of women who stuck to their normal diets was 31 pounds. The average weight gain for women in the calorie-restriction group was 11 pounds. Twenty-three extremely obese women actually lost weight during their pregnancy.
The results seem to support less, not more, weight gain during pregnancy. Women in the calorie-restricted group had fewer C-sections and lower rates of gestational diabetes and hypertension and had retained less weight six weeks after delivery.
Fewer women in the calorie-restricted group delivered newborns weighing more than 10 pounds, which can make deliveries risky for both mother and child. There were no growth-restricted babies in either group.
"Women who are obese when beginning a pregnancy are, by definition, unhealthy," noted Dr. Yvonne Thornton, a clinical professor of obstetrics and gynecology at New York Medical College and the study's lead author. "To say that they should gain even more weight is counterintuitive, and our study bears that out."
Still, Thornton does not favor establishing a one-size-fits-all weight gain number for obese women.
Instead, "we need to focus on making these women healthier by getting them to eat a well-balanced diet, similar to the types of moderate calorie-restricted diets that women with gestational diabetes are put on with no ill effects," she said.
About 35 percent of U.S. women are obese, according to the U.S. Centers for Disease Control and Prevention.
Over the decades, the amount of weight pregnant women have been told to gain has varied. Guidelines from the American College of Obstetrics & Gynecology, which were established in 1986, recommend that underweight women gain 28 to 40 pounds during pregnancy, normal weight women gain 26 to 35 pounds, overweight women gain 15 to 25 pounds and obese women gain 15 pounds. Women carrying twins are told to gain more.
Though doctors know that obesity during pregnancy raises the risk of hypertension, gestational diabetes and other complications, no one is certain what the optimal weight gain for pregnant women should be.
"Over the past decade, obstetricians have become more aware that the idea of 'eating for two' is really not a good thing, especially for patients who start out obese," said Dr. Robin Kalish, director of clinical maternal fetal medicine at New York Presbyterian Hospital/Weill Cornell Medical Center.
The idea for the study came from Thornton's own lifelong struggle with weight. During her first pregnancy in the late 1970s, she gained 67 pounds and hit a peak weight of 225 pounds.
After the pregnancy, she signed up for Weight Watchers and lost 20 pounds, only to become pregnant again.
But with her second child, she continued the focus on nutrition and gained less than a half-pound.
"I was the first test case,'' Thornton said.
SOURCES: Yvonne Thornton, M.D., M.P.H., clinical professor, obstetrics and gynecology, New York Medical College, Valhalla, N.Y.; Robin Kalish, M.D. director, clinical maternal fetal medicine, New York Presbyterian Hospital/Weill Cornell Medical Center, New York City; June 2009, Journal of the National Medical Association