Developmental assessment is the process of mapping a child’s performance compared with children of similar age. The comparison group is obtained from a representative sample of the population that the child comes from. Several factors contribute to performance varying greatly among different population groups. In a multicultural society, it can be challenging to find appropriate benchmarks for these standards. We aim here to highlight what normal developmental parameters are, when and how to assess a child, and when to refer for specialist assessment.

What is child development?

Development is the process by which each child evolves from helpless infancy to independent adulthood. Growth and development of the brain and central nervous system are often termed psychomotor development and is usually divided into four main domains:

  • Gross and fine motor skills
  • Speech and language
  • Social and personal and activities of daily living
  • Performance and cognition.

When the baby develops in the mother’s womb, brain development starts by the fourth week of gestation and progresses rapidly throughout intrauterine life and early childhood. Brain development—the target of developmental surveillance and screening—reflects neurological maturation. It consists of a complex process of cell growth, migration, connection, pruning, and myelination, and it persists through at least the second decade (20 years of age). This fundamental phenomenon, which determines brain development, is a pre-programmed process that occurs in all children.

What is normal development?

The pattern of development is remarkably constant, within fairly broad limits, but the rate at which goals are achieved varies from child to child. Skills are acquired sequentially, with one goal acquired after another. Later goals, often, depending on the achievement of earlier goals within the same field—for example, children must learn to sit independently before they can stand and then walk. Descriptions of normal development, linked to the ability to perform a particular task at a particular age, relate to the performance of the average child. The acquisition of a key performance skill, such as walking, is referred to as a milestone. For each skill, the normal age range for the attainment of the milestone varies widely.

  • A median age is the age at which half a population of children acquire a skill.
  • A limit age is the age at which a skill should have been achieved and is two standard deviations from the mean.

It is important to know which milestones are most consistent. Smiling socially by the age of 8 weeks is a consistent milestone, whereas crawling is not. Crawling occurs at a widely varying time point, and some children with normal development never learn to crawl.

Genetic factors may determine the fundamental developmental potential, but environmental factors have crucial influences on the profile achieved. Positive experiences during early childhood may enhance brain development, particularly in the area of linguistic and social skills. Unfortunately, however, the brain is also vulnerable to various insults, particularly in the early embryonic stages, but also in later life.

Before Birth

  • Early maternal infections, such as rubella, toxoplasma, cytomegalovirus
  • Late maternal infections, such as chicken pox, malaria, HIV
  • Toxins—for example, alcohol, pesticides, radiation, smoking
  • Drugs—for example, anti-cancer or anti-fits medications
After Birth

  • Infections—for example, Brain infections, Virus that attack growing womb like cytomegalovirus
  • Metabolic disorders, such as low sugar, low or high Sodium levels, dehydration
  • Toxins—for example, lead, mercury, arsenic, chlorinated organic compounds, solvents
  • Trauma, especially head injury
  • Severe under stimulation, maltreatment, or domestic violence
  • Malnutrition, especially deficiency of iron, folate, and vitamin D
  • Maternal mental health disorders, most commonly depression

Studies on abandoned Romanian children provide good evidence of how an adverse environment affects brain growth. Children who were institutionalised have smaller brains than those who have adopted abroad or brought up in a family environment, including foster care in Romania. Other studies showed significant gains in cognitive and language skills after abandoned children are taken into care.

What is developmental delay?

Many clinicians use the term “global developmental delay” to mean a significant delay in two or more of the four main developmental domains listed above. The significant delay is defined as performance two or more standard deviations below the mean on age appropriate standardised norm-referenced testing (usually a secondary care procedure). In the United Kingdom and the United States, the term global developmental delay is usually reserved for younger children (typically under 5 years of age).

In the UK learning disability is usually applied to older children, when IQ testing is more valid and reliable (although formal testing of IQ is rarely performed in clinical practice and the child’s assessment is based on functional abilities).

In the US, the term developmental disability or mental retardation is used in the over 5 age group.

The term developmental impairment or disorder covers a heterogeneous group of conditions that start early in life and present with the delay or an abnormal pattern of progression in one or more developmental domain. Children with autism spectrum disorder fall into this category. In this context, the use of the term developmental delay has been challenged because it conveys a message that the child may “catch up,” which is often not true. Nevertheless, it remains in common use because it is well understood by professionals and parents.

How common are developmental problems?

The global developmental delay affects 1-3% of children. About 1% (90-141 per 10,000) of children have an autism spectrum disorder, 1-2% a mild learning disability, 0.3-0.5% a severe learning disability, and 5-10% have a specific learning disability in a single domain.

Why do we need a structured assessment of the development of a child?

Children develop at different rates, and it is important to distinguish those who are within the “normal” range from those who are following a pathological course. We now have good evidence that early identification and early intervention improve the outcomes of children with developmental impairments. A persuasive body of work, which reviewed evidence from neurosciences, developmental psychology, social sciences, epidemiology (including animal and human studies), longitudinal studies, case series, and case reports, describes

  • the importance of the early years in promoting healthy brain development.
  • the scientific understanding of brain development
  • the environments that do not promote healthy development have a cumulative and ongoing negative impact on a range of social, economic, and learning outcomes over the life course
  • those early interventions are an effective way to improve children’s outcomes than later remediation.

Given the importance of the early years, early intervention is crucial. Early intervention seems to be even more important for children with developmental disabilities than for children more generally, because learning is cumulative, and barriers to healthy development early in life impede development at each subsequent stage. Obviously, identification of abnormality must be followed by further action. Children develop relentlessly, and if they are on a deviant path the course becomes more difficult to change as time goes by. Early child health promotion, which includes support for parenting and treatment, is an effective investment that may prevent the need for more intensive, costly, and often less effective intervention later on. A series of systematic reviews of strategies for improving child development in relatively deprived countries, published in the Lancet, found good evidence that interventions at pre-school age are highly cost-effective.

How do children present with developmental problems?

Children with developmental problems may present in several ways:

  • In countries with routine child health surveillance or developmental screening practices, concerns may be raised at scheduled contacts
  • In children with identified risk factors (such as prematurity) who have undergone developmental surveillance, developmental problems may be detected early
  • Parents may recognise a delay or be worried about a child’s behaviour or social skills and seek professional advice (either through their health visitor, public health nurse, or general practitioner)
  • Professionals in daily healthcare setting may recognise deviant patterns of development and highlight their concerns to the family, thus prompting referral
  • Concerns may be detected opportunistically at health contacts for other reasons, such as childhood illnesses if questions are asked about development.

How are children assessed for developmental problems?

Development can be assessed at several levels, depending on the circumstances. Screening is a process to identify children at increased risk of having developmental difficulties that use relatively brief and simple techniques, according to well-recognised criteria. Screening tests are inherently imperfect assessments because they have to balance the risk of missing a child with delays (sensitivity) versus erroneously identifying children without true delays (specificity). Repeating the test after an appropriate time interval, or conducting a secondary screening with a more accurate and specific test, may improve test accuracy.

Primary care practitioners can opportunistically ask flexible questions about a child’s development at every visit where possible, as part of comprehensive medical care. The questions can be like:

  • Do you have any concerns about the way your child is behaving, learning, or developing?
  • Do you have any concerns about the way he or she moves or uses his or her arms or legs?
  • Do you have any concerns about how your child talks and understands what you say?
  • Does your child enjoy playing with toys?
  • Describe what he or she does while playing Has your child ever stopped doing something he or she could previously do?
  • Does your child get along with others?
  • Do you have any concerns about how your child is learning to do things for himself or herself?

Children identified as at risk (often by a health visitor) may be referred for further assessment in primary or secondary care. Currently, standardised developmental screening tools are not routinely used in primary care in India, though a standardised tool (Trivandrum developmental screening chart) is available.

When should a child be referred for specialist assessment?

These indicators suggest that development is seriously disordered and that the child should be promptly referred to us:

Positive indicators (the presence of any of the following)

  • Loss of developmental skills at any age
  • Parental or professional concerns about vision, fixing, or following an object or a confirmed visual impairment at any age (simultaneous referral to paediatric ophthalmology)
  • Hearing loss at any age (simultaneous referral for expert audiological or ear, nose, and throat assessment)
  • Persistently low muscle tone or floppiness
  • No speech by 18 months, especially if the child does not try to communicate by other means such as gestures (simultaneous referral for urgent hearing test)
  • Asymmetry of movements or other features suggestive of cerebral palsy, such as increased muscle tone
  • Persistent toe walking
  • Complex disabilities
  • Head circumference above the 99.6th centile or below 0.4th centile. Also, if circumference has crossed two centiles (up or down) on the appropriate chart or is disproportionate to parental head circumference
  • An assessing clinician who is uncertain about any aspect of assessment but thinks that development may be disordered

Negative indicators (activities that the child cannot do)

  • Sit unsupported by 12 months
  • Walk by 18 months (boys) or 2 years (girls) (check creatine kinase urgently)
  • Walk other than on tiptoes
  • Run by 2.5 years
  • Hold object placed in hand by 5 months (corrected for gestation)
  • Reach for objects by 6 months (corrected for gestation)
  • Point at objects to share interest with others by 2 years

What happens when a child is referred to a specialist?

The child usually has an initial consultation to clarify the nature of the developmental difficulties. Investigations (blood and urine tests, cranial imaging) may be arranged at this stage or later.

The child may then undergo a structured developmental assessment and intervention package of care over 2 to 3 sittings, after which a diagnosis will be reached, a report issued, and recommendations for ongoing support made.

Examples of developmental instruments used in secondary care that are more accurate, sophisticated, and time-consuming (2-3 hours) than those used in primary care include the Griffiths mental development scales, Bayley scales of infant development, and the Wechsler preschool and primary scale of intelligence.


  • Every consultation is an opportunity to ask flexible questions about a child’s development as part of comprehensive medical care
  • Parents who voice concerns about their child’s development are usually right
  • Loss of previously acquired skills (regression) is a red flag and should prompt rapid referral for detailed assessment and investigation
  • Parents and carers are usually more aware of norms for gross motor milestones, such as walking independently, than for milestones and patterns of normal speech, language acquisition, and play skills; so we consider targeted questioning
  • We always consider use of developmental screening questionnaires and measurement tools to supplement clinical judgment

Adapted from BMJ 2013;346:e8687 doi: 10.1136/bmj.e8687