Abstract
BACKGROUND: Preterm birth or shorter gestation is a common adverse pregnancy outcome. Pregnancy-specific anxiety is robustly associated with risk for shorter gestation. Hypothalamic-pituitary-adrenal (HPA) dysregulation, indicated by diurnal cortisol index variability [slope, area-under-the-curve (AUC) or cortisol awakening response (CAR)], could mediate associations between pregnancy-specific anxiety and shorter gestation. The purpose of this study was to explore whether diurnal cortisol index variability mediates associations between pregnancy-specific anxiety and gestational length. METHODS: A sample of 149 women from the Healthy Babies Before Birth study reported pregnancy-specific anxiety in early pregnancy. Saliva samples were taken at three times during pregnancy, for two days each, at wake, 30 min post wake, noon, and evening. Diurnal cortisol indices were calculated using standard approaches. Pregnancy cortisol index variability was calculated across pregnancy timepoints. Gestational length was derived from medical charts. Covariates were sociodemographics, parity and obstetric risk. Mediation models were tested using SPSS PROCESS. RESULTS: There was a significant indirect effect of pregnancy-specific anxiety on gestational length via CAR variability, b(SE)= -0.102(0.057), .95CI [- 0.227,- 0.008]. Higher pregnancy-specific anxiety was associated with lower CAR variability, b(SE)= -0.019(0.008), p = .022, and lower CAR variability was associated with shorter gestation, b(SE)= 5.29(2.64), p = .047. Neither AUC or slope variability mediated associations between pregnancy-specific anxiety and gestational length. CONCLUSION: Lower CAR variability during pregnancy mediated the association between higher pregnancy-specific anxiety and shorter gestational length. Pregnancy-specific anxiety could dysregulate HPA axis activity, as indicated by lower CAR variability, demonstrating the importance of the HPA axis system in regulating pregnancy outcomes.