(Reuters Health) - Women who have had a first-trimester abortion are no more likely to seek psychiatric care after the procedure than before -- but the risk of a mental health problem increases if the woman gives birth, new research shows.

But the study also found that women who had abortions were nearly four times more likely to have sought mental health services in the months before their abortion compared to women who carried their children to term, a finding for which the researchers have no clear explanation.

The study in the New England Journal of Medicine is the latest to assess the psychological impact of early abortion. While proponents say the procedure is safe, opponents promote a long list of psychological problems that, they contend, can surface after the pregnancy is terminated.

The new work was done on a large population database, using medical records on nearly a million girls and women. From that group the research team identified 84,620 who had abortions and 280,930 who gave birth to live babies over a 13-year period.

More importantly, "it didn't rely on women volunteering to tell someone they've had an abortion or to say that they had mental health problems after it," chief author Trine Munk-Olsen of Aarhus University in Denmark said in a telephone interview.

The Munk-Olsen team used the Danish Civil Registration System to identify every female born from 1962 through 1993 and who either delivered their first child or had their first first-trimester abortion from 1995 through 2007.

Among those who had abortions, the researchers found that out of every one thousand women, about 15 sought treatment for psychiatric problems in the nine months before the abortion, and roughly the same number sought treatment in the year afterward.

But among the women who gave birth, about four in every thousand sought help for a mental disorder in the months leading up to delivery, compared to nearly seven per thousand during the one-year period afterward. In other words, nearly twice as many needed psychiatric help after childbirth compared to the period right before they became mothers.

"The risk after childbirth was significantly greater than the risk before childbirth," the team wrote. The risk was highest within a few months after childbirth.

The researchers said the results suggest that the risk factors for needing mental health services in girls or women who seek abortion probably predate the abortion "and indeed may make termination of the pregnancy more likely." they reported.

"We can only really speculate about why" the women who got an abortion had a higher rate of seeking psychiatric help in the first place, Munk-Olsen said. "But we do know that women giving birth constitute a very healthy group of women in general. Perhaps it doesn't really make sense to compare those two groups of women."

The Danish study did not look at milder forms of psychological stress.

"We're looking at psychiatric episodes severe enough for a woman to either be admitted or have an outpatient contact at a clinic," the researcher said. "We do not have information on mild symptoms like depressive symptoms."

For example, a panel appointed by the American Psychological Association reported in 2008 that there was no credible evidence that having one elective abortion of an unwanted pregnancy causes mental health problems for adult women.

But abortion opponents have focused on other research, such as a 2008 New Zealand study that reported on a 30 percent increase in mental disorders for women having abortions.

But in New Zealand, most abortions are done for mental health reasons and the results were based on after-the-fact interviews with women, which could have skewed the results

"Most studies have failed to distinguish between mental health diagnoses such as depression and psychosis, and feelings of sadness, loss, or regret, which, although unpleasant, do not necessarily signify a mental disorder," Munk-Olsen and colleagues said.

SOURCE: bit.ly/g5guqz New England Journal of Medicine, online January 26, 2011.

Abortion in Denmark is legal and freely available up to the 12th week of pregnancy.

Other studies have also reported no psychological impacts from abortion.