| Class | Description |
| A | Abnormal GTT before pregnancy at any age or of any duration treated only by diet therapy |
| B | Onset at age 20 years or older and duration of less than 10 years |
| C | Onset at age 10 to 19 years or duration of 10 to 19 years |
| D | Onset before 10 years of age, duration over 20 years, benign retinopathy, or hypertension (not preeclampsia) |
| R | Proliferative retinopathy or vitreous hemorrhage |
| F | Nephropathy with over 500 mg/day proteinuria |
| RF | Criteria for both classes R and F |
| H | Evidence of arteriosclerotic heart disease |
| T | Prior renal transplantation |
| Gestational diabetes | |
| A1 | Diet-controlled gestational diabetes |
| A2 | Insulin-treated gestational diabetes |
