Motor development of first born compared to later born children in the first two years of life – A replication

Purpose: The motor development of firstborns compared to children having an older sibling in the first two years of life was examined. Method: The data of the study come from an ongoing research project with citizen participation, which is investigating the development of motor milestones in the first and second years of life. Parents report online their children's developmental progress using a development calendar. 18 motor skills from birth until children manage walking alone are recorded, 14 relate to gross motor skills and four to hand motor skills. Results: Children with siblings achieved higher values at birth in terms of Apgar-score, height, weight, BMI and parental satisfaction with the health and development of the child compared to firstborns. However, no differences could be found at the ages of 10-12 months and 14 months. Firstborns reached five fine motor and manual dexterity milestones earlier than children with siblings. In contrast, when mastering 13 gross motor milestones, no differences could be found between firstborns and children with siblings. Conclusion: Motor development at an early age is considered to be largely genetically controlled, analogous to physical development. However, the faster development of the fine motor skills of the firstborns could be related to the fact that parents interact more intensively with their firstborn than with later born children and - unlike gross motor skills - in fine motor skills not only genetic factors but also learning processes are effective from a very early age.