More than two-thirds of pregnancies in unmarried 20-something women between 2001 and 2008 were unplanned, a new study finds.

In 2008 alone, nearly 10 percent of unmarried women ages 20 to 29 experienced an unintended pregnancy. About half of unintended pregnancies in this age group end in abortion, according to the study released Tuesday (April 24) by the non-profit Guttmacher Institute.

The study pulled data on unplanned pregnancy, abortion and miscarriage rates from a multitude of national sources, including the National Center for Health Statistics, the National Survey of Family Growth and the Centers for Disease Control and Prevention. The results revealed that there were 3.4 million pregnancies in women in their 20s between 2001 and 2008. Of these, more than half, or 1.95 million were in unmarried women.

Of those 1.95 million pregnancies, 69 percent were unintentional. The rate was highest in women ages 20 to 24, with 73 percent of pregnancies in this age group unplanned. In women 25 to 29, 63 percent were unplanned.

As of 2008, the researchers report online, 54 percent of births to unmarried women in their 20s were the result of an unintended pregnancy. In comparison, only 31 percent of births among married women were a result of unintended pregnancy. Among all women, about half of pregnancies are unplanned.

"Young people typically have sex for the first time around age 17, but generally don't marry until their mid-20s, putting them at high risk of unintended pregnancy and birth for a decade or more," study researcher Laura Lindberg of Guttmacher said in a statement. "We can't just focus on reducing teen pregnancies anymore. We need to expand our focus to include helping young adult women and their partners reduce their risk through improved contraceptive use." [ Birth Control Quiz: Test Your Knowledge ]

Unplanned pregnancies included pregnancies that were completely unintended as well as pregnancies that occurred two or more years prior to when the women in question would have wanted one.

Women with lower levels of education, women in poverty and black and non-white Hispanic women are at the highest risk for an unmarried, unintended pregnancy, the report found. Black and Hispanic women had twice the rate of unplanned pregnancies as their white counterparts, though black women were the only group over the 2001-2008 time period to see a decline in their rate of unplanned pregnancies.

Women in poverty were three to four times more likely than the highest-income women to experience unplanned pregnancy, and women who had only a high-school diploma were twice as likely as women with some college to get pregnant unintentionally.

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