Long-term stress may increase a woman's risk of infertility, according to a recent study HealthDay reported.

Researchers from Ohio State University Wexner Medical Center found that high levels of stress could reduce a woman's ability to conceive by as much as 29 percent, HealthDay reported.

The study results were published in the March 24 issue of the journal Human Reproduction.

"When we get to couples starting to have problems [conceiving], stress levels really seem to differ from those who get pregnant [quickly]," Courtney Lynch, lead study author and assistant professor of epidemiology, told Fox News.

For the study, researchers followed about 500 reproductively healthy couples who were trying to get pregnant for more than 12 months. During that period, researchers recorded each couple's time-to-pregnancy and observed that by five to six months into the study, the couples "who had yet to conceive were those with the highest levels of chronic stress."

To study stress levels, researchers took saliva samples from women twice - at the start of the study and again after they'd had their first menstrual period during the study time frame.  They "recorded levels of the biomarker salivary alpha-amylase, which measures the body's sympathetic adrenomedullary pathway, more commonly known as the "fight or flight" system. Salivary alpha-amylase levels indicate chronic stress levels.

Of the approximately 400 couples that completed the study, 87 percent of the women became pregnant. After adjusting for age, race, income, and the use of alcohol, caffeine and cigarettes, HealthDay reported. The researchers found that the women with the highest alpha-amylase levels had a 29 percent lower probability of pregnancy compared to the women who had the lowest levels of the enzyme.

Their findings suggest that stress-reducing methods may be beneficial for some couples trying to start a family.

"Stress is not helping you. Whatever you can do to lower that...not only can potentially help you get pregnant faster, but if you start your pregnancy healthier, you'll be a healthier pregnant woman, a healthier post-partum mother," Lynch said.