Heterogeneous cortisol patterns during the peripartum: Insights from a longitudinal trajectory analysis

The maternal hypothalamic-pituitary-adrenal (HPA) axis undergoes substantial physiological changes during pregnancy and postpartum, reflected in altered cortisol secretion patterns. However, research has shown considerable heterogeneity in cortisol patterns across the peripartum period and in part contradictory findings. Individual courses of cortisol secretion and their determinants remain poorly understood.

In a longitudinal cohort of 127 healthy pregnant women, we assessed salivary cortisol at five time points from late pregnancy (gestational weeks 34-36 and 40) to eight weeks postpartum. Group-based trajectory modeling was applied to three cortisol measures to identify distinct cortisol secretion patterns. Associations with sociodemographic and psychological covariates were explored.

Across all cortisol indices, two distinct trajectory groups emerged. The majority of women (79-86 %) exhibited stable, relatively lower cortisol levels during late pregnancy and postpartum, while a smaller subgroup (14-21 %) exhibited a consistently elevated and more variable cortisol trajectory. Trajectory groups showed high classification stability (98-99 %), but no sociodemographic or psychological variables significantly predicted group membership.

Our findings reveal two distinct maternal cortisol trajectory subgroups across the peripartum period, reflecting heterogeneity in HPA axis regulation. The lack of significant associations with the measured covariates raises the possibility that unmeasured mechanisms, such as genetic or epigenetic influences, may contribute to these patterns. These distinct cortisol trajectories may reflect differing modes of neuroendocrine regulation, offering a potential explanation for inconsistencies in prior peripartum cortisol research.