Child development is an extremely complex and long-term process. In order to assess whether this is normal or not, it is important to realise that there are several spheres of development, namely motor development, speech development and social contact. The development of all these spheres should be harmonious and the new functions that the child acquires should appear at a certain time.

The first sphere, namely motor development, includes the successive functions of raising the head on the abdomen, turning around one's own axis (first from the abdomen to the back and then in the opposite direction), crawling, sitting up, crawling and then standing up and walking independently. The last of these appears around 12 months of age. At a later age, these skills are perfected, so the child learns to run efficiently and to stand steadily on one leg. Around the age of five, the child reaches the peak of his or her motor abilities, hence this age is sometimes referred to as the "golden age" in child development. The most common abnormality in motor development identified by parents is a delay in the occurrence of these functions. In some cases, this may be the result of disorders affecting the central or peripheral nervous system.

In some children, however, delayed motor development has a family background or is due to social neglect. Quite often, the development during the first six months of life is not well appreciated by the parents; it is only the lack of independent sitting up after the eighth month of life or the inability to walk on one's own after the 12th month that raises their concern. This is why it is important to ask the paediatrician for an indicative assessment of the child's development at each appointment for a scheduled vaccination.