| p(Twin status|co-twin status) | Co-twin status of tortuosity | ||
| Twin status of tortuosity | Category 1 | Category 2 | Category 3 |
| Category 1 | 0.56 (0.37 to 0.72) | 0.35 (0.22 to 0.51) | 0.10 (0.01 to 0.38) |
| Category 2 | 0.42 (0.26 to 0.60) | 0.51 (0.34 to 0.67) | 0.70 (0.35 to 0.94) |
| Category 3 | 0.02 (0.00 to 0.10) | 0.14 (0.06 to 0.26) | 0.20 (0.01 to 0.58) |
Numbers are given as probability p (95% confidence interval).
Category 1, straight retinal arteries; category 2, wavy retinal arteries; category 3 tortuous retinal arteries.