Final answer:
The coding for a pregnant patient with type 2 gestational diabetes controlled by diet is O24.410.
Step-by-step explanation:
The coding for a pregnant patient with type 2 gestational diabetes controlled by diet is O24.410. This code specifies that the patient has gestational diabetes mellitus in pregnancy, which is a type of diabetes that occurs during pregnancy. The code also indicates that the condition is controlled by diet, meaning the patient is managing their blood glucose levels through dietary changes without the need for medication.