After falling steadily for more than a decade, the birth rate for American teenagers jumped in 2006 for the first time since 1991, health officials at the Centers for Disease Control and Prevention showed on Wednesday.

The number of births to teenage girls in the United States helped to push total births to a 40-year high, reaching nearly 42 births per 1,000, the CDC report said. Researchers calculated about 435,000 births to girls between 15 and 19.

"That finding surprised us because we had a 14-year steady decline in the teen birth rate. Even though the pace of the decline had slowed in the past couple of years, it was still declining, and this year's finding took us off guard," said Stephanie Ventura, head of the Reproductive Statistics Branch at CDC.

The preliminary birth data report also said unmarried childbearing reached a record high in 2006. The number of births to single mothers jumped nearly 8 percent, from 1.52 million in 2005 to 1.64 million in 2006. The birthrate attributed to non-married couples rose 7 percent from 47.5 births per 1,000 unmarried women aged 15 to 44, to 50.6 per 1,000 women. The percentage of births outside marriage also rose, from 36.9 percent to 38.5 percent. Among blacks, they accounted for 70.7 percent of births. Among Hispanic, it was 49.9 percent and among whites 26.6 percent.

Researchers also discovered that the U.S. fertility rate was about 2.1 births per woman of childbearing age over her lifetime. It is the first time since the early 1970s that the rate was above the replacement level, at which a given generation can replace itself, the CDC said.

Ventura qualified the statistics as “concerning” but added that it is too soon to know whether the increase was the beginning of a trend.

"It could be a new trend, but it's just really too soon to say. This early warning should put people on alert to look at the programs that are being used to see what works," Ventura said.

Mary-Jane Wagle, president of Planned Parenthood Los Angeles believes that the increase is due to the failure of abstinence-only education programs, which make teens less aware of contraceptive options.

"Every study shows that abstinence-only funding does not work to reduce teen pregnancy. What Planned Parenthood would have hoped for would be money spent instead on comprehensive sex- education programs," said Wagle, who was not involved in the research.

Some experts blame the rise of the teen birth rate on these programs, which receive about $176 million a year in federal funding. They say that they do not teach use of condoms and other contraception.

"Congress should put the right foot forward and immediately stop funding for dangerous abstinence-only programs that deny young people information about how to prevent pregnancy, protect their health and make responsible decisions," said Cecile Richards, president of Planned Parenthood Federation of America in a statement, according to Reuters.