Researchers at the University of Nottingham analysed saliva samples obtained from 135 women undergoing fertility treatment at the Nurture fertility clinic between December 2012 and April 2014, of which 88 also provided hair samples. Sixty percent of the women reported a successful pregnancy.
After controlling for factors known to be linked to IVF success, such as age, BMI (body mass index), and the number of eggs retrieved and fertilised, the researchers found that while cortisol levels in the saliva samples were not related to pregnancy outcomes, women with high levels of cortisol in their hair were found to be 27 percent less likely to become pregnant than those with low levels of the hormone.
Lead author Professor Kavita Vedhara, from the University of Nottingham's School of Medicine, said the findings 'provide preliminary evidence' that long-term cortisol levels may influence conception rate and that lowering cortisol levels prior to IVF may increase a woman's likelihood of IVF success.
'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. There has been ongoing debate within the scientific community about whether or not stress may influence fertility and pregnancy outcomes,' she said, adding that the findings do not suggest that stress is a direct influence on pregnancy outcomes following IVF.
Previous studies examining the link between cortisol levels and IVF relied on measuring cortisol in saliva, blood, and urine. These measures of cortisol only provide short-term insight, while cortisol levels in the hair may indicate hormone function over three to six months previously.
Commenting on the study, Dr Channa Jayasena, senior lecturer in reproductive endocrinology at Imperial College London and spokesperson for Society for Endocrinology, said: 'An advantage of measuring hormones in the hair is the ability to measure "average" hormone levels over weeks or months without needing a blood test. So the report is really interesting. However, we need other studies to be published before speculating whether this will change fertility treatment for women.'