Many couples have assumed stress was a factor, but now they have verification.
To make the connection, researchers from Ohio State Wexner Medical Center and colleagues at other medical centers followed hundreds of couple for more than a year. The couples weren't known to have fertility problems before the study started.
Researchers measured levels of a stress enzyme in the saliva.
High levels of the enzyme more than doubled the chances of infertility. And the risk rose with each month the couples didn't conceive.
One woman in that study believes she was over-stressed. Before finally getting pregnant with triplets, she was juggling a full-time job and starting a business, while also trying to start a family.
"When you think back to it, when there was nothing else that they could ever actually pinpoint that was wrong, maybe I was manifesting stress, obviously, in a different way," says Abigail David.
Now that doctors KNOW stress can affect fertility, they're hoping to learn more about how stress-relievers such as meditation and yoga can help.
There is no proof it works yet, but most say they're worth a try.