The Third Month's Development Predicts the Side and Oblique Sit and Walking

Background/Objectives: Motor development is endogenously generated until approximately the third month and strongly approximated in all children; hence, this is an excellent time to assess development, both in terms of the achievement of selected milestones (quantitative assessment) and individual single motor elements (qualitative assessment). This article aims to identify which selected milestones and single motor elements performed at the third month and between the fourth and fifth months condition the achievement of the side sit and oblique sit, followed by walking. Methods: All the children (93 infants) underwent prospective evaluations of motor development at 3, 4-5, and 7-8 months of age, with final assessment at 12 months. The three-month development analysis was based on the Quantitative and Qualitative Assessment of Motor Development Worksheet. Results: All the quantitative features showed a statistically significant effect on achieving side and oblique sitting and eventually walking at 12 months, with those studied between the fourth and fifth months being stronger predictors. The distal parts of the upper limbs analyzed in both positions at three months of age have a strong relationship with the side sit, the oblique sit, and walking. Conclusions: Quantitative and qualitative assessments in the third month have predictive value for achievement of side sitting, oblique sitting, and walking. Correct distal upper limb function development is necessary to achieve side and oblique sitting.