Relationship between spontaneous kicking and age of walking attainment in preterm infants with very low birth weight and full-term infants

BACKGROUND AND PURPOSES: Although early kicking differences have been reported for preterm infants without overt cranial sonographic abnormalities, their functional importance remains unclear because no outcomes have been measured. Therefore, the first purpose of this prospective study was to examine the age of walking attainment in preterm infants who had very low birth weight (VLBW) but no overt neurosonographic abnormalities and full-term infants without known impairments or pathology. The second purpose was to examine the relationship between spontaneous kicking and age of walking attainment in these infants. SUBJECTS AND METHODS: Twenty-two preterm infants and 22 full-term infants were examined for kicking movements at 2 and 4 months corrected age and were followed up for age of walking attainment until 18 months corrected age. RESULTS: Survival analysis showed that infants with VLBW attained walking ability at older ages than full-term infants after correction for prematurity. Cox proportional-hazards regression analyses for all infants revealed that a high hip-knee correlation at 2 months corrected age, a high kick frequency at 4 months corrected age, and a short intra-kick pause together with a low variability in interlimb coordination at 2 and 4 months corrected age were all associated with a decreased rate of walking attainment. DISCUSSION AND CONCLUSION: The results indicated that preterm infants who had VLBW but no overt neurosonographic abnormalities had an increased risk of delayed walking attainment compared with full-term infants. Alterations of spontaneous kicking may predict a decreased rate of walking attainment in both preterm and full-term infants.