Background: One of the disadvantages of medical documentation in Electronic Medical Record (EMR) systems is that records tend to be redundant by “copying and pasting”, a writing style to duplicate and revise previous records. In this study, we analyzed the similarity between records to identify the factors affecting the writing style of clinical notes. Method: We analyzed 98,038 records of 4,149 patients from two years in the Department of Obstetricians and Gynecology at Kyoto University Hospital, Japan. We observed the correlation between the distribution of the record similarity and string amounts, as well as the disease codes and ratios of outpatient visit. Results: The patient group with high record similarity and large number of strings was the group with reproductive medicine, followed by the group of malignant tumor follow-up or Women’s Healthcare. Discussion: In reproductive medicine, physicians have a demand for an overarching evaluation, and in follow-up malignancies or in Women’s Healthcare, they have a demand to check for subtle differences from the last time. These facts along with our data insist that the writing style in EMR systems is related to the patient’s status. Conclusion: We declared that the writing style in EMR systems is affected by the patient’s status. The writing style of duplicating and revising is preferred (1) when there is a clinical demand for an overarching evaluation, and (2) when there is a clinical demand to check for subtle differences from the last time.