Here is the design of a clinical trial:

Official Title: Effectiveness of Checklist Based Box System Interventions (CBBSI) on Improving Utilization of Maternal Health Service in North West, Ethiopia: a Cluster Randomized Controlled Trial

Included conditions:
- Maternal Health Service

Study Armgroups:
- {'label': 'Checklist Based Box system', 'type': 'EXPERIMENTAL', 'description': 'Pregnant mothers will receive scheduled person-centered health educations starting from: they are identified as suspected pregnant mother up to attending their third PNC visit. In between the first ANC and the third PNC drop out tracing mechanisms will be applied, for mothers who fail to utilize the recommended maternal health services.', 'interventionNames': ['Other: Checklist Based Box system intervention']}
- {'label': 'Routine maternal health care', 'type': 'NO_INTERVENTION', 'description': 'Pregnant mothers in this arm will receive the usual routine maternal health care.'}

Interventions:
- {'type': 'OTHER', 'name': 'Checklist Based Box system intervention', 'description': 'The intervention has both behavioural change and service utilization drop out tracing mechanism. Special type of boxes designed to schedule health educations and continued service utilization monitoring boxes will be placed at health posts and health centers respectively. Community level survey will be conducted to identify suspected pregnant mothers using stanback et al, 1999 checklist, and mothers are linked to health centers. Then, they will be followed for their subsequent attendance of consecutive maternal health services (ANC 2nd-third PNC). Mothers who fail to utilize the service will be traced; will get person-centered health education to continue the service.', 'armGroupLabels': ['Checklist Based Box system']}

Primary Outcomes:
- {'measure': 'Continued maternal health service utilization (ANC 1-4), Institutional Delivery, PNC (1-3)', 'description': 'Proportion of mothers receiving continued maternal health service (four ANC, skilled birth attendance and PNC three) in the intervention and control clusters, assessed using standard questionnaire', 'timeFrame': '42 days after delivery'}

Please estimate the sample size based on the assumption: 
Number of clusters is 30 (15 per arm), 95% confidence interval, 80% power, and an intracluster correlation coefficient of 0.04849.
Sample size determination
        The sample size was calculated based on the recommendations of sample size calculations for cluster randomized controlled trials with fixed number of clusters [19] by using the following assumptions: utilization of the third PNC in the control group is 16% based on a previous study [20], the number of clusters available is 30 (15 clusters per arm), with 95% confidence interval and 80% power, and an intracluster correlation coefficient of 0.04849 [21]. The sample size was calculated to determine the number of observations required per cluster for a two-sample comparison of proportions (using normal approximation) using STATA software. Assuming individual randomization, the sample size per arm is 194; allowing for cluster randomization, the average cluster size required is 40. A total of 1200 pregnant mothers (600 in the intervention and 600 in the control groups) will be recruited to detect a 12% increase in the utilization of ANC visit four, skilled birth attendance and PNC. The outcome is treated as a binary measure.