Secondary outcomes of the early collaborative intervention EACI on salivary cortisol co regulation in preterm infants and mothers

Abstract The Early Collaborative Intervention (EACI) aims to strengthen early parent–infant relationships among moderate to late preterm infants in neonatal intensive care. This randomized controlled trial evaluated whether EACI influences mother–infant salivary cortisol co-regulation in mother–infant dyads, as well as infant cortisol reactivity and breast milk exposure during early infancy. Secondary outcomes were assessed in 54 dyads in the intervention group and 41 in the standard care group at one and four months’ corrected age. Salivary cortisol was collected before and after a bath at one month and a still-face procedure at four months. Significant mother–infant salivary cortisol co-regulation was observed in the per-protocol intervention group at both time points, whereas no such synchrony emerged in the standard care group. Maternal cortisol levels decreased following stressors in both groups, while infant cortisol reactivity remained unchanged. Although a higher proportion of infants receiving EACI were given breast milk at four months, this difference was only statistically significant in the intention-to-treat analysis. These findings indicate that EACI enhances early mother–infant salivary cortisol co-regulation but does not alter infant cortisol responses to mild or anger stressors. The results highlight the potential of brief, relationship-focused interventions to support early stress-regulatory processes in preterm infants. Trial registration: Evalotte Mörelius, ClinicalTrials.gov NCT: 02034617 (first posted 10/01/2014). Study Details | NCT02034617 | Evaluation of a Parent-Infant Interaction Model | ClinicalTrials.gov.