Here is the design of a clinical trial:

Official Title: Microwave Ablation Versus Radiofrequency Ablation for the Treatment of Severe Complicated Monochorionic Pregnancies in the Peking University Third Hospital : A Pilot Randomised Controlled Trial

Included conditions:
- Twin; Complicating Pregnancy
- Microwave Ablation

Study Armgroups:
- {'label': 'Microwave ablation group', 'type': 'EXPERIMENTAL', 'description': 'Microwave ablation is used for the treatment of Complicated Monochorionic Pregnancies', 'interventionNames': ['Procedure: Microwave ablation']}
- {'label': 'Radiofrequency ablation group', 'type': 'ACTIVE_COMPARATOR', 'description': 'Radiofrequency ablation is used for the treatment of Complicated Monochorionic Pregnancies', 'interventionNames': ['Procedure: Radiofrequency ablation']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Microwave ablation', 'description': 'Use of microwave energy to ablate tissue surrounding fetal umbilical cord. All the procedures are performed percutaneously under ultrasound guidance.', 'armGroupLabels': ['Microwave ablation group']}
- {'type': 'PROCEDURE', 'name': 'Radiofrequency ablation', 'description': 'Use of radiofrequency energy to ablate tissue surrounding fetal umbilical cord. All the procedures are performed percutaneously under ultrasound guidance.', 'armGroupLabels': ['Radiofrequency ablation group']}

Primary Outcomes:
- {'measure': 'Neonatal survival rate', 'description': 'The proportion of live births at 28 days postpartum', 'timeFrame': 'a month after delivery'}

Please estimate the sample size based on the assumption: 
5% (two-sided) type I error, 80% power, 10% non-inferiority margin.
Sample size
        The purpose of this pilot RCT is to explore the feasibility and evaluate the efficacy and safety of MWA reduction for severe complicated monochorionic pregnancies. According to previous studies, the rate of neonatal survival at 28 days of RFA ranged from 63.6% to 88.6% (average 76.0%). Based on the preliminary date of our department, the rate of neonatal survival at 28 days was nearly 73.3% in patients treated with MWA. Thus, a sample size of 878 patients (439 in each group) would be required with a 5% (two-sided) type I error and a power of 80% using a 10% non-inferiority margin. However, based on the feasibility and the intent to provide pilot dates to full sample sizes and statistical plans, 30 participants in each group and a total of 60 participants will be recruited for this trial.