The first research to document unintended pregnancies in the United States since 2001 makes clear that we’ve made little progress in combating that phenomenon.

Researchers at the Guttmacher Institute in New York City pooled data about pregnancy intentions, live births and abortions to establish rates of unintended pregnancies. The paper, published today in the journal Contraception, found that of the 6.7 million pregnancies in 2006, almost half (49 percent) were unintended. While that number is only slightly higher than in 2001 (when it was 48 percent), it indicates that we’re moving in the wrong direction.

The big picture aside, the report also highlighted disparities among socioeconomic groups. The unintended pregnancy rate among poor women ages 15 to 44 has risen from 88 per 1,000 women in 1994 to 132 per 1,000 women in 2006 — a 50-percent increase. At the same time, higher-income women’s unintended pregnancy rate dropped from 34 per 1,000 women in 1994 to 24 per 1,000 in 2006. All told, the unintended pregnancy rate about poor women was five times that of higher-income women and their rate of unintended birth six times as high.

Unintended pregnancy rates were also particularly high for women who were 18 to 24 years old and those who were cohabiting.

While some women who unintentionally become pregnant ultimately embrace those pregnancies, the study notes, such circumstances more often have less-happy consequences. “Women who have an unintended pregnancy,” the authors explain, “are also at risk for unintended childbearing, which is associated with a number of adverse maternal behaviors and child health outcomes, including inadequate or delayed initiation of prenatal care, smoking and drinking during pregnancy, premature birth and lack of breastfeeding, as well as negative physical and mental health effects on children.”

The report does offer a couple of bright notes: The unintended pregnancy rate for 15- to 17-year-olds actually decreased, and the percentage of unintended pregnancies ending in abortion among all women decreased from 47 percent in 2001 to 43 percent in 2006.

The authors suggest that improving access to reliable contraception, especially for high-risk groups such as poor women and women who are cohabiting without being married, is essential to reducing unintended pregnancy rates.