Study Ties Maternal Weight Gain to Child Obesity

(Aug. 4) -- Researchers have already established that excessive maternal weight gain causes babies to be born overweight and increases their lifetime risk of obesity. But a new study has found that the connection persists even when mother and baby aren't genetically predisposed to higher body mass.

Researchers at Children's Hospital Boston, whose work is published online today in The Lancet, looked at the records of 513,501 women in Michigan and New Jersey, all of whom gave birth to two or more children from 1989 to 2003.

Women who gained relatively more weight during pregnancy, 44 to 49 pounds, were 1.7 times more likely to give birth to a baby weighing more than 8.8 pounds. That's the cutoff for "high-birth-weight babies," according to the study.

And since the study's participants all reared at least two kids, researchers were able to control for genetics and compare sibling birth weights. They found that women who gained more weight in subsequent pregnancies gave birth to heavier and heavier babies.

Infants born prematurely or late, as well as mothers with diabetes -- which increases baby's risk of weight problems -- were excluded from the study.

"Since high birth weight, in turn, increases risk for obesity and diseases such as cancer and asthma later in life, these findings have important implications to general public health," study co-author Dr. David Ludwig said in a statement.

The Institute of Medicine advises women to gain no more than 35 pounds during pregnancy, assuming they're of a normal weight at the outset. Overweight women should gain 15 to 25 pounds.

About 55 percent of women at childbearing age are either overweight or obese, and 20 percent of women in a major study of more than 41,000 pregnancies, released last year, gained excess pounds during gestation.

Scientists suspect that excessive weight gain during pregnancy alters key hormones, and maybe even the cells of the pancreas and fat tissue in a developing fetus.

And prudent weight gain during pregnancy makes sense for expectant mothers, too. Excessive gain can cause gestational diabetes and preeclampsia, a potentially fatal blood pressure condition.