ABSTRACT
The gross motor development of a typically developing infant is a dynamic process, the intra-individual variability of which can be investigated through longitudinal assessments. Changes in gross motor development vary, according to the interaction of multiple sub-systems within the child, environment, task setting, and experience or practice of movement. At present, studies on environmental factors that influence gross motor development in full-term infants over time are limited. The main aim of this study was to investigate environmental factors affecting intra-individual variability from birth to 13 months. The gross motor development of 41 full-term infants was longitudinally assessed every month from the age of 15 days using the Alberta Infant Motor Scale. Parents were interviewed monthly about environmental factors during childcare. Infants showed fluctuations in the percentile of gross motor development, and no systematic pattern was detected. The total mean range of gross motor percentile was 65.95 (SD = 15.74; SEM = 2.28). The percentiles of gross motor skills over the 14 assessments ranged from 36 to 93 percentile points. Factors that were significantly associated with the gross motor development percentile were the use of a baby walker (Coef. = -8.83, p ≤ 0.0001) and a baby hammock (Coef. = 7.33, p = 0.04). The use of baby hammocks could increase the gross motor percentile by 7.33 points. Although the usage of a baby walker is common practice in childcare, it may cause a decrease in the gross motor percentile by 8.83 points according to this study. In conclusion, healthy full-term infants exhibited a natural variability in gross motor development. Placing infants in a baby walker during the first year of age should be approached with caution due to the risk of delayed gross motor development.
ABSTRACT
BACKGROUND: The gross motor percentiles of the Alberta Infants Motor Scale (AIMS) have been commonly referenced in research. Cross-cultural assessment of gross motor development during the first year of life is suggested as diverse child-rearing practices can cause inter-variability. The main aim of this study was to develop an AIMS percentile curve for typically developing home-raised infants in the northeastern part of Thailand. The AIMS scores of these infants were also compared with the standard Canadian norms. METHODS: The gross motor development of 574 full-term infants aged 15 days to 14 months was assessed using the Thai version of the AIMS. Percentile curves of their gross motor ability were developed. The Thai infants' mean AIMS scores were compared with the Canadian norm using the one-sample t-test. RESULTS: The percentile curve of gross motor development of healthy Thai infants showed that mean AIMS scores increased with age. Large inter-variability was present from the 7th to 10th months. The mean AIMS scores of Thai infants were significantly lower than the standard Canadian means during the first three months (P < 0.05), but significantly higher in three age groups: 7-<8 months, 11-<12 months, and 13-14 months. CONCLUSION: The developed percentile curve of gross motor development is applicable for infants from the same demographic and environmental context. According to the study, infants from diverse cultures display a natural inter-variability in gross motor development between the 7th and 10th months.
