Young women who have children in their teens are at greater risk of becoming fat than their peers who don’t get pregnant, new research shows.

“Our findings are potentially important because adolescence has been identified as one of the critical periods of development that set the stage for the onset of obesity later in life,” Dr. Erica P. Gunderson of Kaiser Permanente in Oakland, California and her colleagues write in the Archives of Pediatrics and Adolescent Medicine.

For adult women, pregnancy boosts obesity risk, Gunderson and her team note in their report, and there’s evidence that getting pregnant and bearing a child may have an even greater influence on body weight and fat accumulation in adolescents.

To investigate, Gunderson and her colleagues looked at 1,890 women who had enrolled in a national study of growth and health at age 9 or 10 and were followed up every year for up to 10 years.

Seventeen percent had given birth to one child when they were between 15 and 19 years old; 4 percent had more than one child during this time; 10 percent got pregnant but didn’t have a child; and 69 percent didn’t get pregnant.

Forty-three percent of the 983 African-American girls got pregnant in their teens, compared to 19 percent of the 907 white girls.

Overall, at age 18 or 19, 28 percent of the white women and 49 percent of the African-American women were overweight or obese. However, among those who had given birth in their teens, 40 percent of whites and 57 percent of African Americans were overweight or obese.

Among the black women in the study, those who had one or more babies during their teens were heavier and had larger waists, larger hips, and more body fat than their counterparts who did not get pregnant.

Similar trends for waist size and body fat were seen among the white women.

“The excessive fat deposition during adolescence may signal the onset and persistence of obesity and elevated insulin, lipid and blood pressure levels into adulthood,” Gunderson and her team write, noting that women who give birth for the first time before age 20 are also known to be at greater risk of heart disease.

They conclude by calling for further research on the effects of weight gain during teen pregnancy on growth and fat accumulation.

SOURCE: Archives of Pediatrics and Adolescent Medicine, April 2009.