The first thousand days from conception are crucial for future learning and development throughout life. During the infant year, several sensitive periods for sensorimotor, cognitive and social development coincide, making the period particularly suitable for early intervention (EI). From a special educational perspective, the social and physical environment of a child may either support or hinder future growth. Optimal early learning environments include environmental enrichment, reduced toxic stress and strengths-based support of parent-child interaction.

Being born extremely preterm (EPT <28 gestational weeks) is a biological risk factor, increasing the risk for future disability, academic difficulties and social challenges. The parents are also negatively affected by prematurity. Sweden offers highly specialized neonatal care from 22 GW, resulting in a new population of surviving children.

The aim of this thesis is to evaluate an interaction-based and strengths-based EI for infants born EPT and their parents in a Swedish context. The Stockholm Preterm Interaction-Based Intervention (SPIBI) consists of 10 home visits led by a trained interventionist during the first year at home, focusing on parent-child interaction, family strengths and reduction of toxic stress. The control group received an extended treatment as usual follow-up program (TAU⁺). The thesis has a mixed methods design and includes three studies.

Study I presents the protocol, including a description of the planning, formulation, theoretical background, theory of change, interventionist training, recruitment, randomization and implementation of the SPIBI. Study II reports the primary outcome of the RCT (N=130, intervention=66 vs. controls=64) and their parents regarding parent-child interaction as measured with the Emotional Availability Scale (EAS) at 12 months corrected age (CA). The EAS consists of the six dimensions: sensitivity, structuring, non-intrusiveness, non-hostility, child responsiveness and child involvement. No significant effect of the EAS at 12 months CA related to the SPIBI was found. In the secondary analysis, analysis of covariances for all EAS dimensions were tested with predefined medical, social, and psychological moderators. The model with the best fit was one for the EAS dimension child involvement (adj R²=.463). A significant effect modifier shows that the SPIBI enhances child involvement in families where the mothers rate themselves as depressed at discharge (F(1, 65)=5.499, p=.023).The parental experience during the first year at home with or without the SPIBI was qualitatively analyzed and reported in Study III (n=17). The results showed that child-related medical concerns were still present a year post-discharge, and that the premature birth experience still affected the parental inner state and family dynamics. Parents in the intervention group (n=8) also pointed out the security the knowledgeable interventionists gave them, while some parents described the SPIBI as important but not necessary.

Overall, this thesis adds to the understanding of the first year at home with a child born EPT. An interaction-based intervention in the home environment is feasible in Sweden. It is possible to unite different professions in an EI in a special educational context. The tested intervention does not affect the emotional availability at 1 year CA, but findings from secondary analyses prompt further research on specific subgroups, particularly families with depressed mothers.