Continuous subcutaneous insulin infusion (CSII) therapy is widely accepted for brittle type 1 diabetes, since it has the benefit of less frequency of hypoglycemia and better management of the dawn phenomenon compared to multiple daily insulin injection (MDI) therapy. On the other hand, insulin aspart, one of the rapid-acting insulin analogs, was approved for Pregnancy Category B rating by the United States Food and Drug Administration (FDA) in 2007, whereas the FDA created the rating system and approved a Pregnancy Category B rating for human regular insulin in 1979. However, the safety and efficacy of insulin aspart used in CSII therapy has not been established in pregnant type 1 diabetic patients. Here, we report the case of a pregnant patient with brittle type 1 diabetes successfully managed by conversion from MDI therapy to CSII therapy with insulin aspart.