If a mother gains too much weight during her pregnancy she places her child at an increased risk of being overweight farther down the road. This is according to a recent study published in Lancet, England’s premier medical journal. The researchers were American and funded by the U.S. National Institutes of Health. They followed all births in Michigan and New Jersey between the years 1989 and 2003. Of the 513,000 women and 1.1 million infants that were a part of the study, scientists found that women who gained more than 53 pounds during pregnancy gave birth to babies that were about 1/3 of a pound heavier than infants of women who only gained 22 pounds.

Babies that are heavy at birth are at a much higher risk of remaining heavy throughout their lives, according the Dr. David Ludwig, the director of the Optimal Weight for Life program at Children’s Hospital in Boston, and one the study’s authors. They are at a higher risk of other problems later in life, including asthma, allergies and even cancer. They are also more likely to get stuck in the birth canal or to need a cesarean section. When pregnant women overeat, some of the extra calories overstimulate the fetus’s growth. "The fetus is developing in an abnormal metabolic environment where there is excess blood sugar," Ludwig said. "That could alter the development of tissues, organs and perhaps even the wiring of the brain that regulates appetite and metabolism."

Previous studies have shown that pregnant women who gain too much weight are at a higher risk of developing diabetes and high blood pressure. This is some of the first research to demonstrate what those extra pounds may mean for their babies. According to Neal Halfon of the Center for Healthier Children, Families and Communities at the University of California, obesity prevention in the womb is not about trying to get pregnant women to trim down, but to pay attention to their diet and exercise. "This is an extremely important message," said Arne Astrup, a professor of nutrition at the University of Copenhagen. "If mothers are not careful, they could in some way program their children to be obese or diabetic before they are even born."

"It’s never too early to start preventing obesity," according to Stephan Rossner, a professor in the obesity unit at Karolinska Hospital in Sweden who was not connected to the study. "It may be uncomfortable for mothers to eat less and change their lifestyle, but after nine months they will get a great payoff for their children."

In the U.S., more than a third of women of normal weight and more than half of overweight and obese women gain more weight than their doctors recommend.

The Institute of Medicine, an independent, nonprofit organization that advises the U.S. government, says normal-weight women should gain 25 to 35 pounds (11 to 16 kilograms) during pregnancy, while overweight and obese women should gain 11 to 25 pounds (5 to 11 kilograms).