Predictors of early life milestones: Results from the Copenhagen Perinatal Cohort

BACKGROUND: Pre- and postnatal factors have been found to be predictors of age at attaining milestones in infancy; however, the degree to which such factors are predictors of milestones in the subsequent years is less investigated. The aim was to conduct a systematic evaluation of a broad range of possible predictors of milestone attainment during the second and third years to identify factors that explain significant inter-individual variance. METHODS: Mothers of 4009 children from the Copenhagen Perinatal Cohort (1959–61) were interviewed by a physician about 20 developmental milestones at a three-year examination. Milestones were related to: Language, Walking, Eating, Dressing, Social interaction, and Toilet training. Information on possible predictors was collected during pregnancy and at a 1- and 3-year follow-up. RESULTS: Several pre- and postnatal factors were significantly associated with the timing of milestone attainment; especially parental social status, paternal age, sex, gestational age, birth weight, birth length, weight increase in the first year of life, and motor development during the first year of life. The significant predictors explained 16.2% of the variance in the Overall mean of milestones and 20.3% of the variance in milestones related to Walking. The most influential individual factor for the timing of milestone attainment was previous motor development during the first year of life. Additionally, sex was an important factor as girls were generally faster at attaining milestones. Parental social status was a consistent, but relatively week predictor. CONCLUSION: A notable amount of variance in the timing of milestones during the first three years of life can be explained by perinatal and early postnatal factors. The study provides evidence of developmental continuity as the main predictor of milestones in the second and third years was the speed of development during the first year.