Key Facts

Developmental delay is one of the most common reasons for referral to community paediatrics. A systematic approach to investigation, combined with early intervention, improves outcomes for children and families.

Epidemiology

Global developmental delay affects approximately 1-3% of children under 5. Learning disability (intellectual disability) affects approximately 2% of the population. Specific speech and language delay is the most common isolated delay (~5-8%). Autism spectrum disorder affects ~1% of the population.

Aetiology

Prenatal (~50%):

• Genetic: Down syndrome (trisomy 21), fragile X, other chromosomal abnormalities, single gene disorders
• Congenital infections: CMV, toxoplasmosis, rubella, Zika
• Teratogens: Alcohol (FASD), antiepileptics (valproate), recreational drugs
• Structural brain malformations

Perinatal (~15%):

• Birth asphyxia (HIE)
• Prematurity and its complications (IVH, PVL)
• Neonatal sepsis/meningitis

Postnatal (~15%):

• Meningitis/encephalitis, head injury (NAI), metabolic disease
• Environmental deprivation/neglect

Unknown (~20%):

• Despite investigation, cause remains unidentified in ~20-40%

Pathophysiology

Developmental delay reflects impaired or delayed CNS maturation. Genetic causes produce abnormal brain development (neurogenesis, migration, synaptogenesis). Acquired causes (HIE, infection) produce direct neuronal injury. Environmental causes (deprivation) affect synaptogenesis and neural pruning during critical periods.

Patterns of Delay

• Global delay: All/most domains affected — consider genetic, metabolic, structural brain abnormality
• Motor delay: Cerebral palsy, muscular dystrophy, spinal muscular atrophy
• Speech/language delay: Hearing loss, autism, specific language disorder, environmental deprivation
• Social/communication delay: Autism spectrum disorder
• Regression: Loss of previously acquired skills — neurodegenerative disease, Rett syndrome, epileptic encephalopathy

Key History Points

• Pregnancy/birth history (infections, drugs, birth asphyxia, prematurity)
• Family history (consanguinity, learning disability, genetic conditions)
• Developmental milestones in all domains
• Feeding, growth, behaviour
• Parental concerns (always take seriously)

Red Flags

• Developmental regression — urgent investigation
• Dysmorphic features — genetic assessment
• Micro/macrocephaly — measure and plot head circumference
• Seizures with developmental delay — epileptic encephalopathy
• Consanguinity — increased risk of autosomal recessive conditions
• Faltering growth with delay — consider metabolic disease, neglect, FASD

First-Line (All GDD)

• Chromosomal microarray (CMA): First-line genetic test — detects copy number variants; yield ~15-20%
• MRI brain: Structural abnormalities — yield ~30%
• Thyroid function tests: Hypothyroidism (treatable cause)
• Hearing assessment: Formal audiometry
• Vision assessment: Ophthalmology review
• FBC, U&Es, LFTs, ferritin: Baseline

Second-Line (If First-Line Normal)

• Fragile X testing: Especially in boys with GDD + family history
• Whole exome/genome sequencing: Increasingly first-line in NHS; yield ~30-40% when CMA negative
• Metabolic screen: Amino acids, organic acids, acylcarnitine profile, urine mucopolysaccharides, lactate
• CK: If motor delay (muscular dystrophy screening)
• Congenital infection screen: If microcephaly, intracranial calcification, hearing loss

If Regression

• Urgent MRI + MRS: White matter disease, structural change
• EEG: Epileptic encephalopathy
• Metabolic workup: Lactate, ammonia, very long chain fatty acids (VLCFA), white cell enzymes
• Genetic panel: Targeted NGS panels for neurodegeneration

Non-pharmacological

• Early intervention: Begin therapy regardless of whether diagnosis is established
• Physiotherapy: For motor delay — promotes mobility, prevents contractures
• Speech and language therapy: For communication delay
• Occupational therapy: Fine motor skills, ADL support, sensory integration
• Portage: Home-based early learning programme
• Educational support: EHCP (Education, Health and Care Plan) for children with significant needs
• Family support: Parent groups, respite, social care

Pharmacological

• Treat specific underlying conditions (e.g., hypothyroidism, epilepsy)
• Melatonin for sleep disorders in children with developmental delay (common co-morbidity)
• Behavioural management strategies first for challenging behaviour

Referral Criteria

• Not meeting limit-age milestones — community paediatrician
• Developmental regression — urgent paediatric neurology
• Suspected autism — NICE CG128 pathway
• Suspected hearing loss — audiology
• Suspected genetic condition — clinical genetics
• All GDD — multidisciplinary child development centre assessment

• Down syndrome: Mild-moderate learning disability in most; life expectancy ~60 years with modern healthcare
• Cerebral palsy: Varies from minimal disability to severe; GMFCS classification guides prognosis
• FASD: Lifelong neurodevelopmental difficulties; no cure but support improves outcomes
• Autism: Lifelong condition; early intervention improves communication and social skills
• Isolated speech delay: ~50% catch up by age 3; persistent delay may indicate specific language disorder or autism
• Metabolic conditions: Some treatable if identified early (e.g., PKU, hypothyroidism); neurodegenerative conditions have poor prognosis

Developmental Delay Investigation Algorithm

Key Genetic Causes of GDD