Background factors studied; criteria for reduced optimality
| Factor | Optimal |
|---|---|
| Family factors (first degree relatives only) | |
| Speech/language retardation | Absent |
| Learning disorder | Absent |
| Motor clumsiness | Absent |
| Left handedness | Absent |
| Mental retardation | Absent |
| Epilepsy | Absent |
| Tics | Absent |
| Attention deficit | Absent |
| Prenatal factors | |
| Smoking | No |
| Gestational age (weeks) | 37–41 |
| Small for gestational age | No |
| Large for gestational age | No |
| Eclampsia/pre-eclampsia | Absent |
| Antiepileptic drugs | No |
| Severe infections in pregnancy | Absent |
| Alcohol exposure | No |
| Intrapartal factors | |
| Apgar score | 9–10 |
| Vacuum extraction | No |
| Twins or multiple birth | No |
| Breech or foot presentation | No |
| Cord prolapse, around neck/knot | No |
| Child severely traumatised (fractures, lots of petechiae) | No |
| Neonatal factors | |
| Hypoglycaemia | No |
| Septicaemia/meningitis | Absent |
| Respiratory distress | Absent |
| Hyperbilirubinaemia not treated | Absent |
| Hyperbilirubinaemia treated | Absent |
| Difficulties regulating temperature | No |
| Irritable/floppy infant | No |
| Postnatal factors | |
| Encephalitis | Absent |
| Meningitis | Absent |
| Concussion | Absent |
| Convulsions | Absent |
| Social factors | |
| Social class | I, II, or III20 |
| Ethnicity | Parent: Swedish/immigrant |
| Family structure | Parent: married/divorced/single |
| Child living with half siblings | |