Children whose mothers were obese when they became pregnant are at increased risk of becoming obese themselves, according to a new study.

The results highlight the importance of starting early to prevent childhood obesity, the study’s author told Reuters Health.

“Compared to children born to mothers who are of normal weight in early pregnancy, those children born to mothers who are obese in early pregnancy are twice as likely to be obese by the time they reach school age,” said Dr. Robert C. Whitaker of Mathematica Policy Research, Inc., a nonpartisan firm in Princeton, New Jersey.

“Obesity prevention strategies should begin at, or even before, birth,” said Whitaker, who was at the University of Cincinnati College of Medicine and Cincinnati Children’s Hospital Medical Center in Ohio when the study was conducted.

Obesity is well known to run in families, but until now there has been no study on the relationship between a mother’s weight during pregnancy and her child’s odds of becoming obese by preschool age.

Whitaker studied more than 8,000 preschool children who were enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), a federal nutrition program.

More than 30 percent of the children’s mothers had been obese during the first trimester of pregnancy.

By age 4, almost one out of every four children born to an obese mother was obese, compared to fewer than one out of 10 children born to non-obese mothers, Whitaker reports in the online edition of the journal Pediatrics. The risk was increased even after taking into account birth weight.

There are several possible explanations for the apparent link between maternal obesity and an increased risk of child obesity, according to Whitaker. A child may inherit maternal genes that increase the risk of obesity. Another possibility is that a mother’s obesity may somehow affect a child’s development in the womb.

An obese mother may also increase her child’s risk of obesity by the choices she makes about a child’s food and physical activity, Whitaker notes.

The bad news, according to Whitaker, is that many children in WIC are at risk for obesity because so many women in the program are obese.

But a more optimistic attitude is that the period before conception, during pregnancy and a child’s first years all offer “important opportunities to prevent obesity by affecting an intergenerational cycle that promotes obesity,” Whitaker notes in the report.

SOURCE: Pediatrics, July 2004.