A pilot project was conducted to test the study design for a large, cohort, multi-center, prospective, descriptive study of the midwifery model of care using an online data registry. Data collection was done using the American Association of Birth Centers‟ online data registry, the Uniform Data Set®. Instrument validity was evaluated by conducting site visits to compare data from health records with data in the data registry. Analysis was done for a limited data set for five sites comprised of thirty-six variables from the comprehensive data registry. Site visits were conducted in five midwifery practices that had been entering data into the data registry for at least three years and 177 randomly selected records were reviewed. Comparison of the data entered in the UDS® with data in the medical records showed consistent entries for 97.3% of the variables reviewed, while 2.7% were inconsistent. All variables showed over 90% consistency, with ten variables 100% consistent. Strategies for improving data quality are identified. Data analysis was done on aggregate data from 6,200 records from the five practices in order to evaluate data quality and estimate time and resources needed for data cleaning and analysis in the larger study. Characteristics of the population are described, as well as key outcomes. Specific variables needing further clarification for users of the data registry include all those describing transfers to acute care for mother or infant.