Pre-existing type 1 diabetes, in pregnancy, third trimester

This code signifies a pregnant patient in her third trimester who has a pre-existing diagnosis of type 1 diabetes mellitus. It indicates that the diabetes was present prior to the current pregnancy, rather than being gestational in origin. The code reflects the ongoing management of this chronic condition during the final stage of pregnancy.

Apply this code for pregnant patients with a documented history of type 1 diabetes mellitus who are currently in their third trimester. Documentation should clearly state the pre-existing nature of the diabetes and the current gestational stage. This code is appropriate for encounters related to monitoring and managing the patient's diabetes during this period.

• Always sequence this code as a primary diagnosis when the encounter is for the management of the diabetes during pregnancy.
• Do not confuse with codes for gestational diabetes (O24.4-) or pre-existing type 2 diabetes (O24.1-).
• Ensure the medical record explicitly states "pre-existing type 1 diabetes" and "third trimester" to support code assignment.