Variations in early gross motor milestones and in the age of walking in Japanese children.

BACKGROUND: Gross motor development is usually assessed in terms of age of achievement of motor milestones. Although there is generally an impression of faster development if the milestones are achieved at younger ages, no longitudinal studies have been done on the associations between the milestones, especially in Japan. As a part of the Japan Children's Study, the purpose of the present study was to determine whether the achievement of gross motor milestones in infancy is related with the age of walking. METHODS: This was a prospective cohort study of 290 healthy and term infants born in a district of Osaka City, Japan. Three milestones (rolling over, sitting, and crawling) were observed in the laboratory for infants aged at 4 and 9 months by a pediatrician and a developmental psychologist, and the age of walking was confirmed in questionnaires filled in by the parents at 18 and 27 months. RESULTS: Children who could roll over at 4 months, and sit and crawl at 9 months, walked earlier than children who could not roll over, sit and crawl, respectively. With regard to crawling, children who were creeping had a 1 month delay in walking, and those who could not move forward had a 2 month delay compared to typical crawlers. On multiple regression analysis these three milestones were positively associated with walking: rolling over (ß= 0.567), sitting (ß= 1.973) and crawling (ß= 1.473). CONCLUSION: The age and the patterns of sitting, crawling and rolling over were all related to the age of independent walking among Japanese infants. Consideration of milestone definition and variations is essential in medical check-up.

Head growth evaluation in early childhood, from the Japan Children's Study.

BACKGROUND: Head circumference (HC) trajectories are held to reflect neurological development and the acquirement of intelligence. It is important to assess HC growth accurately because atypical HC growth is an indicator of various developmental disorders. HC growth is determined by both familial and physical factors but, hitherto, no one has considered both factors together. The aim of the present study was thus to investigate the relationship between HC, physical growth, and parental HC. METHODS: The study group in the Japan Children's Study consisted of 192 healthy full-term Japanese children. HC (maximum occiptofrontal circumference), height and bodyweight were measured at the ages of 4, 9 and 18 months. Multiple regression analysis were conducted predicting the HC from the body measurements and mid-parental HC (defined as the average of standardized paternal and maternal HC). RESULTS: Adjusted multiple R(2) were 0.336, 0.307 and 0.259, measured at the aforementioned three stages. Bodyweight and mid-parental HC predicted the HC on each occasion (P < 0.01). Bodyweight was more relevant than mid-parental HC. CONCLUSIONS: HC growth is influenced by physical growth and parental HC; therefore, it is important to consider both physical and familial factors. A formula is herein proposed to assess HC using bodyweight and mid-parental HC.

[Laterality of upper extremity movements in infancy: observations at 4 and 9 months of age].

This study investigated the process involved in the lateralization of movements during infancy by observing upper extremity movements in a laboratory setting. Reaching for flying rings, balls, mini toy cars, and small round cookies were observed and recorded by videotape at 4 and 9 months of age. The subjects were 202 infants who participated in Japan Children's Study, a cohort study on the development of sociability. Infants reached for objects significantly more frequently at 9 months (98%) than at 4 months (40%) (p<0.001). Though the lateral preference in reaching for balls at 4 months was ambiguous, reaching for toy cars was performed more frequently with the right hand at 9 months (50%) than with the left one (19%) (p<0.01). Lateralization of the upper extremity movements is thought to appear by 9 months.