LOS ANGELES — Repeat births among teenagers have fallen, but nearly 1 in 5 children born to teen mothers already has a sibling, according to the Centers for Disease Control and Prevention (CDC).

Of more than 367,000 births to mothers 15 to 19 years old in 2010, 18.3 percent were repeat births, a decrease of 6.2 percent from 2007, the CDC reported.

Large disparities among racial and ethnic groups and geographic areas remain, the CDC reported. American Indian or Alaska Native teens registered the highest percentages, 21.6 percent, followed by Hispanics, 20.9 percent, and non-Hispanic blacks, 20.4 percent. The lowest rate was among non-Hispanic whites, 14.8 percent.

“Repeat births can negatively impact the mother’s education and job opportunities as well as the health of the next generation,” said CDC Director Tom Frieden.

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Rates varied from a high of 22 percent in Texas to 10 percent in New Hampshire.

The data come amid a 41 percent decline in pregnancies among U.S. teens, from 1991 to 2010, according to the CDC.

New data show that nearly 91 percent of teen mothers who were sexually active used some form of contraception in the postpartum period. But only 22 percent used contraceptives considered to be “most effective” — those that result in fewer than one pregnancy among 100 users.