Age of sitting unsupported and independent walking in very low birth weight preterm infants with normal motor development at 2 years

Aims: The aims of this study is to (i) determine the age of sitting unsupported and independent walking in preterm infants with birth weight under 1500 g (very low birth weight, VLBW); (ii) estimate differences between VLBW children and a reference population and (iii) estimate the association between clinical characteristics and late age at sitting and walking. Methods: A longitudinal study was conducted of a cohort of 876 children with VLBW. The World Health Organization (WHO) motor development study population was used as a reference. Ages for both skills were established by interview with parents. Means were compared with t-test, ANOVA and Bonferroni adjustment where appropriate. Results: The inclusion criteria were complied with 694 patients; 50% of VLBW sat at 7 m corrected age (CA) and walked at 13 m CA. Both motor skills were acquired later (7.3 +/- 1.5 and 13.6 +/- 2.8 m) compared with the control group (6 +/- 1.1 and 12.1 +/- 1.8 m). Weight or head circumference at birth below the 10th percentile or the presence of bronchopulmonary dysplasia were associated with delayed acquisition of both skills. Conclusion: Very low birth weight infants typically sit unsupported and walk later than term infants. Tables describing reference values for milestones acquisition for different categories of infants (gestational age, birth weight and other determinants) may contribute to inform the decision making process on access to available resources.