Table 1.
Key factors that defined and differentiated the 4 study groups.
| Features shared between sibling pairs | Study Groups | |||
|---|---|---|---|---|
| 1. Monozygotic twins | 2. Dizygotic twins | 3. Full-siblings | 4. Half-siblings with the same birth mother | |
| 9 pairs | 39 pairs | 27 pairs | 9 pairs | |
| Birth mother | identical | identical | identical | identical |
| Birth father | identical | identical | identical | different |
| Genome shared | ~100% | ~50% | ~50% | ~25% |
| Prenatal alcohol exposure | virtually identical | virtually identical | 100% same Rank | 100% same Rank |
| Other prenatal risks | virtually identical | virtually identical | 100% same Rank | 88% same Rank |
| Siblings raised together | 100% | 100% | 96% | 100% |
| Other postnatal risks | 100% same Rank | 87% same Rank | 83% same Rank | 75% same Rank |
| Matched in age within one of 3 age-ranges (0–3; 4–8, 9+ years) | 100% | 100% | *93% | *89% |
*
2 pairs of full-siblings and 1 pair of half-siblings had one sibling that was in a younger age category. In each of these 3 pairs, the younger sibling had the more severe FASD diagnostic outcome.