Here is the design of a clinical trial:

Official Title: Fast-track Referral for Health Interventions During Pregnancy: a Randomized Pragmatic Experimental Study to Reduce Low Birthweight in Portugal

Included conditions:
- Infant, Low Birth Weight

Study Armgroups:
- {'label': 'Intervention', 'type': 'EXPERIMENTAL', 'description': 'Women who present at least one of the four risk factors - smoking, risk alcohol consumption, risk of depression, physical violence - will be eligible to receive the intervention. The intervention will be the activation of fast-track referral for specialized units and care programs for the four psychosocial and behavioural risk factors under study. All pregnant women referred by the "STOP LBW project" would have access to consultations or other health activities, such as counselling and group meetings, within a maximum of seven days, in reference services available in each metropolitan area. The activation of the fast-track referral will be the responsibility of the doctor/nurse who applies the questionnaires to identify the risk factors. The intervention ends with childbirth, abortion or if the participant decides to abandon the study.', 'interventionNames': ['Other: Fast-track referral for reference services']}
- {'label': 'Standard of care', 'type': 'NO_INTERVENTION', 'description': 'Women who present at least one of the risk factors - smoking, risk alcohol consumption, risk of depression, physical violence - will receive the standard of care currently existing in each PHCU. The standard of care varies across the various PHCU and may include several approaches: routine screening with care by the antenatal care provider; routine screening with referral to other health professional in the same health unit; and routine screening with referral to other health services, with the time elapsed for consultation depending on the health resources available in each area. In each PHCU, different standards of care may exist for each of the four risk factors.'}

Interventions:
- {'type': 'OTHER', 'name': 'Fast-track referral for reference services', 'description': 'Activation of fast-track referral for specialized units and care programs for the four psychosocial and behavioural risk factors under study.', 'armGroupLabels': ['Intervention']}

Primary Outcomes:
- {'measure': 'Low birthweight', 'description': 'Incidence of live births with birthweight \\< 2500g', 'timeFrame': 'At birth'}

Please estimate the sample size based on the assumption: 
Bilateral tests, significance level of 5%, statistical power of 80%, institutional adherence rate of 50%, intracluster correlation coefficient of 0.01, and a size variation of 20% in clusters.
Sample size
        We calculated the sample size considering the use of bilateral tests, for a significance level of 5% and statistical power of 80%, in order to compare the intervention and control groups in relation to the primary outcome defined in the main objective of the study. We assume that the intervention can reduce the incidence of LBW by about 30%, that is, from 9.0% to 6.5%. Estimating an institutional adherence rate of 50%, using an intracluster correlation coefficient of 0.01 (estimated from perinatal health studies in primary healthcare)60 and estimating a size variation of 20% in clusters (variation in the number of eligible pregnant women in each PHCU), we calculated a sample size of 1416 participants per intervention/control group, in a total of 2832 participants with at least one risk factor.