We know a fair amount about the women who obtain abortions.

We know when abortions happen, usually in the first trimester. We know where they happen, occurring more often in states with more liberal abortion laws. We know a bit about who gets them, as lower-income and minority women tend to have higher abortion rates.

We know a lot less, however, about women who seek out an abortion but don't receive the service. They don't get counted in the abortion statistics. At least, not until now.

A new research project at the University of California at San Francisco is studying a group of 231 women who were turned away from 30 abortion clinics across the country. Dubbed the Turnaway Project, its researchers recruited women who had shown up at an abortion clinic days after its limit on gestational period had passed. It compares those women, who carried their pregnancies to term, with others who had abortions.

The demographics of the women in the two groups were nearly identical at the time they arrived at the abortion clinics, with 45 percent receiving public assistance and two-thirds living below the poverty line.

One year later though, the researchers started seeing big differences, which they detailed in a recent presentation to the American Public Health Association.

They found that 76 percent of the women who were denied abortions were receiving public assistance, compared with 44 percent of those who were not. Sixty-seven percent were living below the poverty line, 11 points above those who received abortions.

Women who did not receive abortions were also less likely to be working -- 48 percent versus 58 percent of those in the group that did receive abortions.

Annalee Newitz talked to the study authors recently about their other findings, on how these women felt about their decisions:

As the researchers said at the American Public Health Association Meeting, "One week after seeking abortion, 97% of women who obtained an abortion felt that abortion was the right decision; 65% of turnaways still wished they had been able to obtain an abortion." Also one week after being denied an abortion, turnaways told the researchers that they had more feelings of anxiety than the women who had abortions.

Women who had abortions overwhelmingly reported feeling relieved (90%), though many also felt sad and guilty afterwards. All of these feelings faded naturally over time in both groups, however. A year later, there were no differences in anxiety or depression between the two groups.

The Turnaway Project is still a work-in-progress, with two of the five years in the longitudinal study completed. The initial findings seem to suggest some significant but hitherto unrecorded differences between those who obtain abortions and those who do not.