Stress may affect some women's chances of becoming pregnant, a new study suggests.

Researchers found that women who had higher levels of an enzyme in their saliva called alpha-amylase, an indicator of stress, took longer to conceive. The study is the first to show a link between infertility in women and stress levels measured in saliva.  

"We showed that women who had the highest levels of alpha-amylase were more than twice as likely to not become pregnant after 12 months as women who had the lowest amounts," said study author Courtney Lynch, a reproductive epidemiologist at The Ohio State University College of Medicine.

The findings also suggest that the effects of stress seemed to show up after couples had been trying for five months to become pregnant. The researchers found that women's odds of becoming pregnant at the outset were fairly similar regardless of their alpha-amylase levels, but after five months, women with the highest levels of alpha-amylase began to have lower odds of becoming pregnant.

"The study's key finding is an apparent association between preconception stress and the probability of getting pregnant," Lynch told Live Science.

The study was published online on March 24 in the journal Human Reproduction.

Stress and infertility

To explore the role stress may play in women's ability to conceive, the researchers looked at 501 couples in the United States. These couples had no prior history of infertility and had been trying to have a baby for no more than two months.

To evaluate stress, the researchers measured the women's levels of alpha-amylase and cortisol, another saliva-based biological marker of stress, and both men and women kept a daily journal of their perceived stress levels. [Blossoming Body: 8 Odd Changes That Happen During Pregnancy]

The women gave two saliva samples during the 12-month study. One sample was taken the morning after the women enrolled in the project, before they ate, drank, smoked or brushed their teeth — habits known to influence alpha-amylase production. A second sample was collected the morning after the women had their first menstrual period during the study.

Of the 401 couples who completed the study, 347 of them became pregnant.

The results revealed that women who had the highest levels of alpha-amylase were 29 percent less likely to become pregnant than women with the lowest levels. But the data showed no relationship between a woman's cortisol levels and her chances of conceiving.

Although cortisol and alpha-amylase are both indicators of stress, they work in two different biological pathways, Lynch said. Levels of cortisol are more representative of chronic stress, so differences in cortisol levels may not have turned up because saliva tests were done only during the early months of the study, she said.

Managing stress

The role that stress may play in infertility, and the mechanism by which it may influence a woman's chances of having a baby, are complicated.

It's been suggested that couples who are struggling to become pregnant feel more stressed and have sex less frequently. But the new research found no evidence that couples who were unable to conceive had sex less often than couples who were able to conceive. 

"This study indicates that if a couple has not gotten pregnant after five to six months of trying, it may be stress-related," Lynch said.

She encouraged women who are trying to conceive to look into stress-reduction techniques. Those relaxation methods may include mindfulness meditation, yoga, regular physical activity or breathing exercises.

Lynch said researchers don't yet know which relaxation approaches may work best in improving the chances of conceiving. She also pointed out that high stress levels are neither the only nor the most important factor in predicting a woman's ability to become pregnant.

"We have no hard evidence that stress-management techniques may be helpful, but it wouldn't hurt for women to give one of them a try," Lynch said.

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