A LONGITUDINAL STUDY OF THE FREE CORTISOL INDEX IN PREGNANCY

Summary Total plasma cortisol, the ‘cortisol resin uptake ratio’ (cortisol RUR), and ‘free cortisol index’ (FCI) were estimated in 23 pregnant women from 12 weeks to term and at six weeks post partum. Total plasma cortisol rose continually throughout pregnancy; the cortisol RUR rose up to 20 to 23 weeks and then fell slowly and the FCI also rose although more slowly than the total cortisol. All parameters fell to non-pregnant levels at six weeks post partum. It is confirmed that a true rise in metabolically active cortisol occurs during pregnancy.