ObjectiveThe purpose of this study was to examine the relationship between intraindividual changes in cortisol responsiveness over pregnancy and the length of human gestation.Study designPregnancy-related changes in the cortisol awakening response (CAR), which is a measure of hypothalamic-pituitary-adrenal axis responsiveness, were assessed prospectively in 101 pregnant women at 16.8 +/- 1.4 weeks' and 31.4 +/- 1.3 weeks' (+/-SD) gestation. Cortisol was measured in saliva that was collected immediately and +30, +45 and +60 minutes after awakening.ResultsThe CAR was significant in pregnancy and exhibited progressive attenuation over the course of gestation. A larger CAR in late pregnancy and reduced attenuation of the CAR from early to late gestation were associated significantly with shorter gestational length.ConclusionThe findings are the first to suggest that the hormonal (cortisol) response to a naturally occurring challenge (awakening) and the degree of attenuation of this response over the course of gestation may represent a novel biomarker of increased vulnerability for earlier birth
