Main findings
Measures of cortisol in hair clearly demonstrate an increase in cortisol levels throughout pregnancy with a peak around childbirth. This is in line with prior reports based on salivary cortisol, and supports the validity of measurement of cortisol in hair samples since these levels mirror the activity of the HPA axis throughout pregnancy. In the third trimester the increase in hair cortisol was significantly more pronounced in women expecting their first child compared to multiparae that showed a decrease in hair cortisol three months prior to childbirth.