FRIDAY, Oct. 31, 2008 (HealthDay News) -- The more weight a woman gains during pregnancy, the more likely she is to have a large baby, posing health risks to both mother and child, a new study finds.
Women who gained more than 40 pounds -- the maximum recommended pregnancy weight gain -- had twice the risk of having a baby weighing more than 9 pounds, the researchers said.
An estimated one-fifth of women in the study put on too much weight during pregnancy, according to the research, published in the November issue of Obstetrics & Gynecology and funded by the American Diabetes Association.
Less than 12 percent of women who gained weight within the normal range had heavy babies, the study authors said.
"Our study provides one more good reason for all women that they gain the ideal amount of weight during pregnancy, and for the health-care provider to do a good job counseling women about healthy weight gain," said lead author Dr. Teresa Hillier, an endocrinologist and senior investigator with Kaiser Permanente Center for Health Research in Oregon and Hawaii.
Babies too heavy at birth can suffer stuck shoulders and broken collar bones, and are prone to overweight or obesity and type 2 diabetes later in life. And a big baby poses risks for the mother, including vaginal tearing, bleeding and often the need for a Caesarean section, the study authors said.
Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, called the new research "a really good study."
"It shows how you can modify your risk factors for having large-for-gestational-age babies," she said. "Mothers want to be careful how much weight they gain during pregnancy, especially if they have gestational diabetes."
Doctors have known for decades that gestational diabetes -- which is diabetes discovered for the first time when a woman is pregnant -- is a risk factor for having a heavy baby. Treating gestational diabetes reduces the chances of having a large baby by more than 50 percent, the researchers said.
For the study, the researchers looked at 41,540 pregnant women in the Pacific Northwest and in Hawaii, all belonging to the Kaiser Permanente health plan. All underwent glucose screening for gestational diabetes.
The higher the maternal blood sugar levels went, the higher the risk for a heavy baby. Women who gained more than 40 pounds had nearly double the risk of a large baby for each level of blood sugar, compared to women who gained less than 40 pounds.
"Mothers who had normal sugar and gained in excess of 40 pounds had a higher risk of a large baby than women with gestational diabetes who had less sugar [meaning the diabetes was treated] and gained less than 40 pounds," Wu said.
But Hillier offered this caution: "Not gaining enough [weight during pregnancy] is a risk for the baby as well. The focus should be eating healthfully: low-fat dairy, protein, lots of fruits and vegetables, also, under the guidance of a physician, getting moderate amounts of exercise," she said.
For more on a healthy pregnancy, visit the U.S. National Women's Health Information Center.