The findings suggest there is a connection between lifestyle choices and the effectiveness of in vitro fertilization. Photo by nevodka/Shutterstock.com

NOTTINGHAM, England, Oct. 19 (UPI) -- Levels of a specific hormone measured in hair may alter the likelihood of pregnancy in women undergoing in vitro fertilization, scientists in England suggest.

According to researchers at the University of Nottingham, elevated levels of cortisol, often referred to as the "stress hormone," may make IVF conception more difficult. In a study published in the journal Psychoneuroendocrinology, high concentrations of cortisol measured in hair were associated with almost a third less chance of conceiving.


While saliva, urine and blood can be tested for short-term cortisol levels, hair can reveal the cumulative levels of the hormone over 3 to 6 months.

Authors of the study say their findings provide the first substantial evidence cortisol, a hormone affected by lifestyle choices such as diet and exercise, directly affects reproductive outcomes. Reducing levels of cortisol, they add, can improve the chances of a successful IVF pregnancy.

"Researchers have been interested in the role that cortisol may play in determining reproductive outcomes for some time now, not least because cortisol is typically elevated in relation to stress," lead researcher Kavita Vedhara said in a press release. "There has been ongoing debate within the scientific community about whether or not stress may influence fertility and pregnancy outcomes."

Saliva samples from 135 women recruited from a fertility clinic were collected over a 2-day period in the experiment, and 88 of the women provided hair samples. Among all the women, 60 percent conceived following IVF treatment.

While salivary cortisol measurements were found to be unrelated to pregnancy, hair cortisol concentrations were. According to the study, 27 percent of the variance in pregnancy outcomes were accounted for by cortisol concentrations.

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"While these results do not specifically implicate stress they do provide preliminary evidence that long term cortisol levels are associated with a reduced likelihood of conceiving," Vedhara added.

The research team is calling for additional research to verify their findings, noting other factors might play a role in successful IVF conception.

In vitro fertilization is a procedure used to treat fertility problems or assist individuals conceiving a child. The technique has been hailed as the most effective form of assisted reproduction, and can be done using a mother's eggs with her partner's sperm.