As part of the Longitudinal Investigation of Fertility and the Environment Study, researchers tracked 501 American women ages 18 to 40 years who were free from known fertility problems and had just started trying to conceive and followed them for 12 months or until they became pregnant. Saliva samples were collected from participants the morning following enrollment and again the morning following the first day of their first study-observed menstrual cycle. Specimens were available for 373 women and were measured for the presence of salivary alpha-amylase and cortisol, two biomarkers of stress.
"This is now the second study in which we have demonstrated that women with high levels of the stress biomarker salivary alpha-amylase have a lower probability of becoming pregnant, compared to women with low levels of this biomarker. For the first time, we've shown that this effect is potentially clinically meaningful, as it's associated with a greater than two-fold increased risk of infertility among these women," said Lynch, the principal investigator of the LIFE Study's psychological stress protocol.