Stressed out women have more difficulty getting pregnant than women with less stress, according to a new study this week in the journal Human Reproduction.
Although the relationship between stress and trouble getting pregnant has been hinted at before, it had never been scientifically proven before now. This new research marks the first time that scientists have found a direct link between stress and infertility.
"Women should not look at these findings and feel guilty," said Courtney Denning-Johnson Lynch, director of reproductive epidemiology at the Ohio State University Wexner Medical Center, and the lead author of the paper. "They should look at it as an opportunity. Working on stress is something they can try to do on their own to improve their chances of getting pregnant."
She added that stress by no means is the most important factor in whether a woman gets pregnant. "Blocked tubes, or ovulation problems, or the quality of the sperm on the male side has more of an effect than stress," she said.
But the link is there. In a study that followed more than 400 women just as they were starting to try to get pregnant, the researchers found that women with the highest levels of the stress indicator alpha-amylase in their saliva were 29 percent less likely to get pregnant than women with the lowest levels.
They also found that women with the highest levels of alpha-amylase were more than twice as likely to meet the clinical definition of infertility - meaning they did not get pregnant even after a full year of trying.
The researchers still do not understand exactly why stress affects a woman's ability to become pregnant, but this study did rule out some possibilities. "It's not that stressed out women have less intercourse," Lynch said.
They also found no correlation between high levels of alpha-amylase and ovulation problems.
One theory the researchers plan to explore in future studies is whether stress changes what Lynch called "the hormonal milieu" of the uterus in such a way that it becomes inhospitable to implantation.
"But that's still a big question mark," she said.