In a study for evidence that stress reduces the likelihood of a woman getting pregnant, researchers found that women with the highest levels of adrenalin were 12% less likely to conceive in the first month.
Participants in the study were 274 women aged 18-40.
Adrenalin and cortisol levels were measured by the presence of biological markers in their saliva.
The women were asked to keep a diary of menstruation and lifestyle habits.
Adrenalin levels were the only links to reduced conception.