(CNN) — If you’re trying to get pregnant, relax and try to keep your stress down. That sounds like good advice, which your doctor has probably given you, but there has been very little science to back it up – until now.
Researchers, publishing in the journal Human Reproduction, say they have put out the first prospective study showing an association between stress and infertility. They measured stress using biomarkers in the saliva of women who wanted to conceive, and found a strong correlation with alpha-amylase.
“The women who had the highest levels of this salivary stress biomarker had a 29% decreased probability of pregnancy over time, and that actually translated into a more than two-fold risk of infertility for them by the end of the study,” said lead author Courtney Lynch, director of reproductive epidemiology at The Ohio State University Wexner Medical Center.
The National Institutes of Health already recommends reducing stress while trying to conceive, but this new research actually studied the relationship between stress and fertility, Lynch said. Four years ago, Lynch and colleagues showed in a previous study that women with higher levels of a stress biomarker in their saliva had a 15% lower chance of getting pregnant in the first cycle.
Keep in mind that these studies show associations, not causes. Researchers did not investigate why stress might lead to infertility, and there could be some other factor that links the two. And there are many other reasons that a couple may be having trouble conceiving.
In this study, 401 couples completed the entire protocol. Researchers followed the couples for up to 12 months as the couples tried to conceive. Those who got pregnant were also followed during the course of pregnancy. Out of 401 women who went through the entire study, 87% (347) became pregnant and 54 (13%) did not.
All of the women who participated were between ages 18 and 40, were married or in a committed relationship, had recently stopped using contraception and had a male partner aged 18 or above.
Researchers controlled for the age, race, and income of participants, as well as use of alcohol, caffeine and cigarettes while the women were trying to conceive.
Women gave saliva samples the morning after they enrolled in the study and another the morning after their first period during the course of the study. Researchers tested their saliva for the stress biomarkers cortisol and alpha-amylase.
When beginning the study, women answered a variety of lifestyle questions including one that required them to rate their overall daily stress level.
On a daily basis, couples kept a journal, writing down their stress levels as well as whether they had intercourse or experienced menstruation.
Information was collected between 2005 and 2009 as part of the LIFE Study.
Researchers found that women with the most alpha-amylase had a two-fold increased risk of infertility. There was no association with the other stress biomarker tested, the hormone cortisol.
Based on self-reporting, the women in this study seemed to have lower levels of stress than the general population, so even those with the highest levels of alpha-amylase in the study are likely experiencing a relatively low-level of stress, Lynch said.
Although typically couples are seen as having infertility problems if conception doesn’t happen after a year, researchers in the new study saw a steep drop-off after five to six months. After that time, women with higher stress biomarker levels seem to have a much lower likelihood of becoming pregnant.
“We’re suggesting that the five to six-month window is a really an opportunity for women to step back at that point and say, ‘Wow, you know, maybe I ought to consider stress as a potential issue for me.’ “
The study does not suggest that stress is the most important factor in determining whether a couple will conceive, Lynch said. Medical problems and semen quality would be more likely to influence fertility.
But if stress does affect fertility, why? Study authors ruled out the idea that stressed-out women are having less intercourse, based on participants’ journal reports and alpha-amylase levels. There are many theories about how stress could impact fertility more directly, but science has not backed up any yet.
Stress may have increased for some women as more time went by without conceiving, but that would not have been recorded in this study.
The study did not repeatedly collect saliva samples over time. And although participants reported their levels of stress over time in their journals, researchers did not take this information into account in the results. Lynch said self-reported stress levels will be analyzed in a subsequent study.
Interestingly, it is not clear that the self-reported levels of stress correlate with measurable stress biomarkers. In their previous study, Lynch and colleagues noted this discrepancy – “We could not find a paper-and-pencil questionnaire that predicted this well,” she said.
Researchers would also like to know more about who the women are who are experiencing stress-related fertility problems. Are they more anxious and depressed in general, and less resilient to new stressors? That would be a subject for further study.
Lynch and colleagues are working on a randomized controlled trial of a stress intervention to see if that helps women get pregnant faster if they are having stress issues.
In the meantime, if you’re a woman having trouble conceiving after at least five or six months, Lynch recommends trying a proven stress-reducing activity such as mindfulness techniques, meditation, and moderate daily exercise.
“Until we have more data, I think that is the reasonable recommendation to make to women,” she said.
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