pregnancy

A pregnant woman is seen by a midwife. A recent study looked at how a mother's weight gain and blood sugar during pregnancy can affect their child's risk of obesity. (CLAUDIO SANTANA/AFP/GettyImages)

(AFP)

A baby born at a normal size but to a mother who gained too much weight during pregnancy is more likely to be overweight or obese, a new study found.

The study, released Friday, analyzed how a woman's weight and blood sugar levels during pregnancy can affect her child's risk of becoming overweight or obese, even when the child was born within the range of a "normal" birth weight.

The study found that normal-weight babies whose mothers had the highest blood sugar levels were 30 percent more likely to be obese or overweight during childhood. Those whose mothers had excessive weight gain were 15 percent more likely to be overweight or obese.

Researchers already knew that a mother's high blood sugar and weight gain can result in a heavy baby with an increased risk of obesity, the study said. Babies born at a low birth weight are also at greater risk for obesity. For the latest study, researchers focused on babies born at 5.5 to 8.8 pounds, considered the range for a normal birth weight.

"You can't just assume they are normal based on their birth weight," said Teresa Hillier, endocrinologist and senior investigator with Kaiser Permanente's Center for Health Research and study author.

The study, said to be the largest conducted on the topic, followed more than 24,000 mothers and their children over the course of 10 years. Of the children born to those mothers, some were excluded from the study sample for various reasons, including if the baby had low birth weight, the study said. The mothers and babies were Kaiser Permanente members in Oregon, Hawaii and Washington.

Ultimately, the study tracked 13,037 normal weight babies born between the years 1995 and 2003. To calculate body mass index, researchers measured each child's height and weight an average of 9.5 times between the ages of 2 and 10. Mothers were screened for gestational diabetes and weighed multiple times, Hillier said.

All of the children who were born to mothers who had elevated blood sugar levels during pregnancy were at a higher risk of obesity, the study found. But children whose mothers had gestational diabetes, the highest levels of elevated blood sugar, were at least 30 percent more likely to be overweight in comparison to children whose mothers had normal blood sugar levels.

Researchers also evaluated the effects of a mother's excessive weight gain, noting that the Institute of Medicine recommends that women gain no more than 40 pounds during pregnancy. The study found that children whose mothers' weight gain hit or surpassed that benchmark were at least 15 percent more likely to be overweight or obese. Gaining less than 40 pounds would have prevented childhood obesity in about 426 children tracked for the study, authors wrote.

The increases in a mother's blood sugar and excessive weight gain appeared to have affected her child's metabolism, causing an "imprint" for obesity, Hillier said. The babies were adapting to either too much weight or too much sugar.

"There is a critical window in pregnancy where nutrition alters the metabolism in some way that permanently alters it for the baby," Hillier said. "Somehow, the baby is sensing an overfed environment."

Other factors aside from pregnancy weight gain and blood sugar levels, such as poor exercise and lack of access to healthy foods, can also affect a child's risk of obesity, Kaiser Permanente said in a statement. The Centers for Disease Control and Prevention reported that more than a third of children and adolescents were overweight or obese in 2012.

The study shows that what happens to a child's metabolism in the womb may be equally as important as their care after they are born, according to a statement. Hillier hopes the study will show women that they can work with their healthcare providers to help their babies get "the best metabolic chances."

"There's something they can do during their pregnancy that can potentially make a big impact in improving their child's long term health," Hillier said. "For future mothers, we can intervene to help them have a healthy pregnancy."

The study was published in the Maternal and Child Health Journal.

--Laura Frazier

lfrazier@oregonian.com

503-294-4035

@frazier_laura