Diurnal cortisol throughout pregnancy and its association with maternal depressive symptoms and birth outcomes

Depression during pregnancy is a common complication that can negatively affect fetal health and birth outcomes. Cortisol is believed to be a key mediator of this association. Although pregnancy entails a natural increase in cortisol levels, preclinical depression could alter its circadian rhythm, producing excessively high overall diurnal cortisol levels that might be harmful for the fetus and future offspring development. Using a prospective longitudinal design, we aimed to study (i) trimestral cortisol circadian rhythm and its overall levels throughout pregnancy in healthy women, (ii) the extent to which maternal depressive symptoms influence both cortisol rhythmicity and overall levels, and (iii) the possible adverse consequences of elevated maternal cortisol on the offspring's weight and gestational age at birth. 112 healthy pregnant women from the general Spanish population were recruited before their first pregnancy. To assess cortisol circadian rhythm, participants provided four saliva samples at each trimester of pregnancy (at awakening, 30 min after awakening, before lunch and before going to bed). Overall cortisol levels were calculated with AUCg approximation. Depressive symptoms were evaluated in each trimester and defined according to EPDS cut-off values (1st trimester, EPDS ≥ 11; 2nd and 3rd trimesters, EPDS ≥ 10). At birth, the risk for low weight, prematurity and weight birth percentile was retrieved for 100 infants. Mixed models and simple effects were employed to study changes of maternal cortisol circadian rhythm and overall levels throughout pregnancy and the possible influence of maternal depressive symptoms. Finally, logistic regressions were performed to assess the associations between maternal overall cortisol levels in each trimester of pregnancy and birth anthropometrics. Although overall diurnal cortisol levels increase throughout pregnancy, cortisol circadian rhythm is preserved in all trimesters [1st (F(3110)= 92.565, p