A study conducted by Indian-origin researcher found that elevated levels of 'stress hormone' cortisol measured in hair can predict success rate of conceiving through In Vitro Fertilisation (IVF).

The findings suggests that the levels of a hormone when measured in hair can significantly predict the likelihood of pregnancy in women undergoing IVF treatment.

The study was published in the journal Psychoneuroendocrinology.

This technique provides more reliable measure of hormonal function compared to other techniques using saliva, blood and urine that measure only short term levels of the hormone.

The study provide the first proper evidence that long-term levels of cortisol, which are affected by many lifestyle factors including diet, exercise, caffeine and most notably stress, may play an important role in determining reproductive outcomes.

A total of 135 women were observed for the study, 60 per cent of whom became pregnant following IVF treatment. Eightyeight women provided hair samples and the rest submitted salivary samples for the measurement of cortisol.

After analysing both types of cortisol data, researchers found that short-term salivary cortisol measurements were not related to pregnancy but in contrast the hair cortisol concentrations were.

The findings suggest that 27 per cent of the variance in pregnancy outcome was accounted for by hair cortisol concentrations after controlling for other known factors that are linked to IVF success such as age, body mass index (BMI), number of eggs retrieved and the number of eggs fertilised.

"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," said lead researcher Kavita Vedhara, Professor at the University of Nottingham School of Medicine.

"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. A range of factors are likely to account for that, stress being one possibility," Vedhara added.