Here is the design of a clinical trial:

Official Title: Effectiveness of a Home-based Peer Support Program for Chinese Mothers With Low Breastfeeding Self-efficacy to Increase the Exclusivity and Duration of Breastfeeding: a Randomized Controlled Trial

Included conditions:
- Breastfeeding

Study Armgroups:
- {'label': 'Online Home-based peer support intervention', 'type': 'EXPERIMENTAL', 'description': 'Participants will receive intervention on top of standard usual care.', 'interventionNames': ['Behavioral: Online Home-based peer support']}
- {'label': 'Standard usual care', 'type': 'NO_INTERVENTION', 'description': 'Participants will receive standard usual care.'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Online Home-based peer support', 'description': "Online Home-based peer support will be provided to support participants' breastfeeding. There will be a minimum of 2 and maximum of 3 home visits between trained peer counsellors and participants. Each session will last approximately 30 minutes.", 'armGroupLabels': ['Online Home-based peer support intervention']}

Primary Outcomes:
- {'measure': 'Infant Feeding Status: Exclusive Breastfeeding', 'description': 'Number/ proportion of participants who practice exclusive breastfeeding at 1 months postpartum.', 'timeFrame': 'At 1 month postpartum'}
- {'measure': 'Infant Feeding Status: Exclusive Breastfeeding', 'description': 'Number/ proportion of participants who practiced exclusive breastfeeding at 2 month postpartum.', 'timeFrame': 'At 2 months postpartum'}
- {'measure': 'Infant Feeding Status: Exclusive Breastfeeding', 'description': 'Number/ proportion of participants that practice exclusive breastfeeding at 4 months postpartum.', 'timeFrame': 'At 4 months postpartum'}
- {'measure': 'Infant Feeding Status: Exclusive Breastfeeding', 'description': 'Number/ proportion of participants that practice exclusive breastfeeding at 6 months postpartum.', 'timeFrame': 'At 6 months postpartum'}

Please estimate the sample size based on the assumption: 
A power of 80%, a significance level of 5%, and an attrition rate of 30% were used.
Sample size
        The exclusive breastfeeding rate in Hong Kong was 26.3% at 6 months by the time of project initiation.24 To calculate the sample size, a power of 80% and a significant level of 5% were used. Assuming a conservative participation rate of 25% based on our pilot study.23 It is estimated that a sample size of at least 442 participants would be required (n=221 per group), allowing for an attrition rate of 30%.