Women undergoing certain infertility treatments are more likely to become pregnant if they take part in a simultaneous stress reduction program, new research shows.

The finding, published in the journal Fertility and Sterility, raises new and controversial questions about the role that stress may play in infertility.

The issue is a delicate one because historically, doctors often laid the blame for a couple’s inability to conceive on psychological and emotional issues in one or both partners. But research shows that most infertility is the result of physical problems in a man’s or woman’s reproductive system, and psychological factors are rarely the primary cause.

“It’s an extremely sensitive topic for couples,’’ said Alice D. Domar, a psychologist at Beth Israel Deaconess Medical Center in Boston and director of mind-body services at Boston IVF, a large fertility center. “The most common, unwelcome piece of advice to couples is ‘just relax and you’ll get pregnant.’ ”

Even so, a diagnosis of infertility can cause considerable stress and sadness, and patients often report high levels of depression and anxiety. Some studies have compared the stress of infertility to that experienced by patients with cancer or heart disease.

To assess the effects of high levels of stress, researchers are studying whether stress may make the body a less hospitable place for a pregnancy and somehow interfere with the success of fertility treatments. Many large infertility programs offer individual and couples counseling to help men and women cope with the diagnosis and treatment, but it’s not known if any particular type or duration of treatment may affect success rates.

To find out, Dr. Domar and colleagues recruited 100 Boston women under 40 who were taking part in in vitro fertilization, or I.V.F., in which embryos formed in test tubes are implanted in a woman’s body to help her become pregnant.

The women were randomized to a control group that received only the fertility treatment or a group that received fertility treatment as well as a 10-week stress management program that focused on cognitive behavioral therapy, relaxation training and social support.

Researchers tracked the groups through two I.V.F. cycles. In the first cycle, there were no differences in conception rates between the groups. Dr. Domar said that only about half of the women in the mind-body treatment group had begun the program, and those who had started had completed only a few sessions.

In the second cycle, most of the patients had attended at least five mind-body sessions. At that point, 52 percent of the women participating in the stress reduction program had become pregnant, compared with 20 percent in the control group.

“It’s not that it’s all in your mind,’’ Dr. Domar said. “If you’re really stressed out and depressed, the body seems to sense that’s not a good time to get pregnant. There’s something about practicing relaxation techniques or being with other women who understand what you’re going through, probably a combination of everything, that makes a difference. It isn’t just about relaxing.”

The mind-body program includes an exercise called “cognitive restructuring,” in which women are asked to share recurring negative thoughts. Common thoughts include “I’m never going to be happy unless I have a baby,’’ or “It’s my fault for waiting too long.”

Through a series of exercises, the patients are taught to replace the negative feeling with a more positive but still realistic thought — for example, “I’m doing everything I can to have a healthy baby.’’

“For a lot of patients, cognitive restructuring is a huge breakthrough,’’ said Dr. Domar. “Helping them tap into the hope they have is a really powerful thing, and you wouldn’t do an I.V.F. cycle unless part of you believed it would work.’’

Most sexually active women use contraception, regardless of their religious beliefs, says a report from the Guttmacher Institute, an organization working to advance reproductive and sexual health  in the U.S. and worldwide.

“Regardless of religious affiliation, the majority of women use highly effective contraception methods, so any efforts to restrict access to these methods is going to impact these populations,” said Rachel K. Jones, the lead author.

The report was based on a U.S. government survey that represented the nation. The data came from 2006-2008 interviews of over 7,000 women aged 15-44.

It found that 69% of sexually active women from any denomination were using highly effective birth control methods including sterilization, the pill or other hormonal method, or an intrauterine device (IUD). In addition, almost all have reported contraceptive use at some point, a figure that is similar among Catholic women.

Another key finding was that 68% of Catholics use one of the highly effective methods, but only 2% rely on natural family planning. That number is comparable to 73% of Mainline Protestants and 74% of Evangelicals.

“A lot of times, religion is either not associated with contraception at all, or, in the case of the Catholic church, being against contraception.” Jones added. “In the real world, women who have religious beliefs and who attend church also use contraception.”

In addition, male or female sterilization was most common in the Evangelical church; more than four in 10 women of this denomination use the method.

And marital status did not change things.

“Across religious denominations, married women are using highly effective contraceptive methods,” she said.

Said Cecile Richards, president of Planned Parenthood Federation of America, “These findings show yet again that birth control is a common practice — and a common need — for women of different faiths and backgrounds.

“As Congress considers yet another effort to bar Planned Parenthood from providing family planning services through federal health programs, it should listen to the message these findings convey.”