A Guttmacher Institute report released Tuesday shows pregnancy and abortion rates among US teenage girls have increased for the first time in more than a decade. The analysis included data on teenage sex and births collected by CDC's National Center for Health Statistics and figures on abortions collected by CDC and Guttmacher.

Between 2005 and 2006, the pregnancy rate among females ages 15-19 rose 3 percent - the first increase since 1990. The abortion rate among teens rose 1 percent in 2006 from the previous year, also the first increase in more than a decade, according to the non-profit reproductive health think-tank.

"The decline in teen pregnancy has stopped, and in fact has turned around," said Lawrence Finer, director of domestic research at Guttmacher. "These data are certainly cause for concern."

What is driving the jump is the subject of debate, with some experts blaming abstinence-only sex education and others pointing to factors such as AIDS complacency, an increase in poverty, and an over-sexualized culture. "It could be a lot of things coming together," said Rebecca Maynard, professor of economics and social policy at the University of Pennsylvania.

After steady increases in the 1970s and 1980s, teen sexual activity slowed around 1991, cutting the US teen pregnancy rate to historic lows. The decline in teen sex began to level off roughly nine years ago, and the teen birth rate began to increase in 2005. However, it was not known whether this was due to more pregnancies or fewer abortions or miscarriages. The Guttmacher analysis is the first to use those factors to calculate the teen pregnancy rate.