Timing, Sequence, and Windows of Achievement of Motor Development Steps (Milestones) in the First Two Years of Life

Aims / Background: This longitudinal study analyzes the development of 18 gross and fine motor development steps (milestones) in the first two years of life. It also explores the connection between motor development and anthropometric, social, and familial parameters. Of special interest is not only the speed of development but also the sequence of milestones, the windows of achievement, and whether this sequence differs between individuals and different groups. Design / Method: The data come from a research project involving more than 3400 parents, primarily in Germany. Using a Citizen Science approach, parents reported their children's developmental progress online using an observation sheet that charts 14 gross and 4 fine motor skills from birth to the point when children can walk. Despite the non-randomness, most characteristics of our sample were similar to representative German data. Norms for the milestones were calculated for all children and for children born with average birth weight and underweight (less than 2500 g). Results / Conclusion: The sequence and windows of achievement for motor development steps in the first years of life are similar for individuals and for girls and boys. The windows of achievement overlap clearly and vary in width, and not all children master the developmental steps in the same sequence. Gender, type of delivery, nutrition, siblings, mother´s age, parental social status, and month of birth did not affect motor development. However, preterm or underweight newborns showed significantly delayed motor development compared with those with normal birth weight; however, the sequence of motor development was nearly the same. The findings on the impact of environmental and social factors on elementary motor milestones suggest that the motor development in early childhood is predominantly genetically controlled, with environmental factors and childcare practices beeing less important.