Background and aims: In this study we made a detailed analysis of the mothers' release pattern of adrenocorticotropic hormone (ACTH) and cortisol during a breastfeeding session during the second day postpartum and related these patterns to maternal oxytocin levels as well to the duration of sucking and the duration of skin-to-skin contact before sucking the breast. Furthermore, we investigated if epidural analgesia and oxytocin administration during and after labor influenced the release pattern of ACTH and cortisol.
Methods: Sixty-three primiparae were included in the study. Fourteen received oxytocin intramuscularly postpartum, nine received oxytocin infusion, 14 received epidural analgesia combined with oxytocin infusion, and six received epidural analgesia alone. Twenty mothers did not receive any of these medical interventions. Blood samples were analyzed for ACTH and cortisol by enzyme-linked immunoassay.
Results: Both ACTH and cortisol levels fell significantly during the breastfeeding session. A significant negative relationship was found between oxytocin and ACTH levels, but not between oxytocin and cortisol levels. A positive and significant relationship was found between ACTH and cortisol levels. The duration of skin-to-skin contact before onset of sucking was significantly and negatively associated with lower cortisol levels, but not with ACTH levels. Cortisol levels differed significantly between mothers having received epidural analgesia with and without oxytocin.
Conclusions: Breastfeeding is associated with a decrease of ACTH and cortisol levels. Skin-to-skin contact contributes to this effect. ACTH correlated negatively with the duration of sucking and with median oxytocin levels, whereas cortisol levels correlated inversely with the duration of skin-to-skin contact preceding sucking, suggesting a partial dissociation between the mechanisms regulating ACTH and cortisol release. In addition, medical interventions in connection with birth influence the activity of the hypothalamic-pituitary-adrenal axis 2 days after birth.