| Frequency | Mean | |
|---|---|---|
| Infant Characteristics | ||
| Males | 2 | |
| Females | 4 | |
| Twins | 2 | |
| Mean age at assessment | 15.3 weeks | |
| Birth Related Factors | ||
| Firstborn | 3 | |
| Normal delivery | 5 | |
| Vacuum extraction | 1 | |
| Mean birth weight | 3,284 grams | |
| Mean gestational age | 38.8 weeks | |
| Other Suspected Determinants | ||
| Cranial flat spot at birth | 0 | |
| Exhibited side preference | 3 | |
| Only bottle fed | 3 | |
| Always placed supine | 2 | |
| No infant pillow when sleeping supine | 2 | |