Over four years, 401 women who were stopping contraception and trying to have a baby underwent saliva testing for two stress-related substances: the enzyme alpha-amylase, and the hormone cortisol. The women provided a saliva sample upon enrollment in the study, and then another at their first observed menstrual period, so that comparisons between the women could be made from the same starting point.
Researchers analyzed the samples and then followed the women to see how long it took them to become pregnant. Women who became pregnant during the first month of the study (before they could give a second saliva sample) were also included in the analysis.
The scientists defined infertility as a failure to become pregnant after 12 months of unprotected intercourse. During the study, published Monday in Human Reproduction, 347 women became pregnant and 54 did not.
There was no association of cortisol with fertility. But those whose alpha-amylase levels were in the highest third, a sign of longstanding stress, had more than double the risk of infertility. The scientists controlled for age, race, income and other health and socioeconomic factors.
The lead author, Courtney D. Lynch, director of reproductive epidemiology at Ohio State University, said that if a woman was having difficulty becoming pregnant, it would be harmless, and might be helpful, to consider stress-reduction techniques.
"Yoga, meditation, mindfulness have been successful in other health outcomes," she said, "and might be helpful for fertility as well."