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.