Here is the design of a clinical trial:

Official Title: A Culturally-tailored Personalized Nutrition Intervention in South Asian Women at Risk of Gestational Diabetes Mellitus

Included conditions:
- Diabetes, Gestational

Study Armgroups:
- {'label': 'Dietary Intervention', 'type': 'EXPERIMENTAL', 'description': 'A personalized nutrition plan will be developed for each woman and will respect faith-based food choices and regional preferences. The plan will be delivered by a culturally congruent health coach, and consider baseline dietary intake, energy balance for recommended gestational weight gain, personal values and preferences, through setting 2-4 "SMART" goals. Participants assigned to the intervention group will receive text messages. Participants assigned to the intervention group will be given a Fitbit to track their steps and will receive simple text messages weekly, aimed at increasing walking. They will be given PDF resources that provide advice on healthy eating, physical activity, and other lifestyle factors during pregnancy plus additional materials adapted specifically for the South Asian community.', 'interventionNames': ['Behavioral: Dietary Intervention']}
- {'label': 'Control', 'type': 'ACTIVE_COMPARATOR', 'description': 'Participants in the control group will receive simple text messages weekly, aimed at increasing walking. They will be given PDF resources that provide advice on healthy eating, physical activity, and other lifestyle factors during pregnancy plus additional materials adapted specifically for the South Asian community.', 'interventionNames': ['Behavioral: Control']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Dietary Intervention', 'description': 'Individualized diet advice will be developed for each participant by a dietitian familiar with South Asian foods.', 'armGroupLabels': ['Dietary Intervention']}
- {'type': 'BEHAVIORAL', 'name': 'Control', 'description': 'Control group participants will be provided with PDFs, website links to encourage healthy eating, physical activity, and other lifestyle factors during pregnancy. They will also receive weekly text messages aimed at increasing walking.', 'armGroupLabels': ['Control']}

Primary Outcomes:
- {'measure': 'Glucose area-under-the-curve (glucose AUC)', 'description': 'A measure of glycemic response, glucose AUC is a continuous measure of the response to a 75-g oral glucose tolerance test, and is calculated by the trapezoidal method using the fasting, 1-h, and 2-h glucose.', 'timeFrame': '3 months'}

Please estimate the sample size based on the assumption: 
The study assumes a 90% power, a 10% loss to follow-up, and 70% adherence to the intervention. The significance level is not explicitly mentioned but is typically assumed to be 0.05 in clinical trials.
Sample size
        With 86 participants per group (total n=172), the study will have 90% power to detect at least a 15% between-group difference in AUC glucose, the primary outcome, assuming 70% adherence to the intervention (ie, goal setting, health coach contacts, food tracking) and SD of AUC glucose=173âmmol/min.14 A change in glucose of at least this magnitude has been observed in trials of similar design to test fibre supplements,30 high-protein31 or high-fat diets.32 A 10% loss to follow up is assumed, which is low for dietary interventions; however, given the frequent expected contact with healthcare providers during pregnancy, the virtual nature of our intervention and our pilot data,33 it is believed to be feasible. The sample size has been inflated to 95 per group (total n=190) to account for the expected high lost to follow up. The study will have low power to detect a moderate treatment effect on the secondary outcome of GDM (ie, 20%â30%âbetween-treatment difference) and higher power to detect very large treatment effects in GDM (ie, 80% power to detect a 61% relative risk reduction). The study will look to see if GDM incidence, measured as a dichotomous outcome, is nominally improved.