Here is the design of a clinical trial:

Official Title: Stockholm Preterm Interaction-Based Intervention

Included conditions:
- Extreme Prematurity

Study Armgroups:
- {'label': 'Stockholm Preterm Interaction-Based Intervention (SPIBI)', 'type': 'EXPERIMENTAL', 'description': 'Home-based post-discharge intervention for extreme premature babies and their parents. The intervention consists of one hospital visit, nine home-visits and two telephone calls during the first year corrected age, specifically from one week before discharge to 12 months corrected age. The intervention is strengths-based working with the infant-parent interaction, supporting infant development and strengthening the parent in his/her role.', 'interventionNames': ['Behavioral: Stockholm Preterm Interaction-Based Intervention (SPIBI)']}
- {'label': 'Control', 'type': 'NO_INTERVENTION', 'description': 'The participants of the Control Group receives treatment as usual, which consists of a regular follow-up program with neurodevelopmental assessment at term age, 3 months corrected age, 12 months corrected age, 24 months corrected age and 66 months corrected age. Compared to children not participating in the study, the control group will receive an extended follow-up program, with assessment and questionnaires at term age, 3 months corrected age, 12 months corrected age, 24 months corrected age and 36 months corrected age. Participants in the control group will be referred to specialized care when needed.'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Stockholm Preterm Interaction-Based Intervention (SPIBI)', 'description': 'Post-discharge intervention to extreme premature infants and their parents', 'armGroupLabels': ['Stockholm Preterm Interaction-Based Intervention (SPIBI)']}

Primary Outcomes:
- {'measure': 'Parent-child interaction', 'description': 'Emotional availability scales, EAS The scale has four parental dimensions; sensitivity, structure, non-intrusiveness, non-hostility and two child dimensions; child responsiveness and child involvement. Each subscale has a maximum score of 29 and a direct score of 1-7. Hypothesis of higher scores in intervention group.', 'timeFrame': '12 months corrected age.'}

Please estimate the sample size based on the assumption: 
The study assumes a power of 0.8, a significance level (alpha) of 0.05, and a normal distribution.
Sample size and statistical power
        The hospitals in Stockholm treat more than 100 extremely preterm infants every year, but several of them are not residents of Stockholm County, which is a prerequisite for study inclusion. The study team is prepared to recruit 130 participants, 50% of which will be randomized to the SPIBI intervention. The sample size is based on feasibility, and the assumption is that the effect size of the intervention on the primary outcome measure Emotional Availability Scales (EAS) will be moderate, i.e., Cohenâs dâ=â0.5. This is largely in line with the results of Flierman et al. [50] for the sensitivity scale of the EAS in the previously mentioned Dutch trial. Hence, we aim to recruit 130 participants, which gives us a power of 0.8 given a normal distribution and an alpha value of 0.05.