Mary Hardimon. Global Developmental Delay, Don't Forget the Bubbles, 2019. Available at:
Erin is a 3-year old girl who is brought in by her mother, having been screened by the child health nurse as being developmentally delayed (and subsequently referred by GP). Her mother had noted that Erin was “slower than her other kids,” although presumed she was a “late bloomer” who would “catch up in her own time.”
What is global developmental delay (GDD)?
The terminology used around abnormalities in the normal progression of development – like many things in medicine – is problematic, with contention amongst some that “developmental disability” rather than “developmental delay” may be more appropriate.1 Irrespective of preferred terminology, currently financial supportive agencies such as the National Disability Insurance Service (NDIS) categorise as developmental delay.2
Global developmental delay is significant delay seen across multiple domains of function and adaptation, whereby significant is defined as a performance >2 standard deviations below the mean.3 This delay may represent delay in acquisition of milestones or development of milestones which are achieved but qualitatively different.1
Not all children with GDD will meet criteria for intellectual impairment.4
How common is it?
Approximately 1 – 3% of children under the age of 5 years is estimated to be affected by GDD.6, 7
What causes it?
How long is a piece of string! Whilst establishing the aetiology may not alter the medical management of the child, it often provides a number of advantages for the family including:
- Providing information about the diagnostic condition and prognosis
- Allow appropriate genetic counseling for recurrence risk (and risk for other family members)
- Limiting further testing
- Providing “answers” for the family and potentially removing (although may also exacerbate!) guilt
- May lessen co-morbidity by identifying factors likely to cause secondary disability that are potentially preventable Surveillance of other systems such as vision/hearing
- Allow access to more support Within specific syndrome support groups
- Potential condition-specific treatment
It should be noted that upwards of 50% of individuals may not have a cause for their GDD established despite investigation.8
Categorization of aetiology of GDD 3,7, 8
|Genetic/syndromal||Trisomy 21, Angelman’s, tuberous sclerosis||Dysmorphism, multiple organ systems||Point mutations will not be picked up on CGH array|
|Metabolic||Aminoacidopathies, mitochondrial, UCDs, lysosomal storage and glycogen storage disease||Consanguinity, FHx early death, symptom free interval, coarse facial features, organomegaly||Rare cause of GDD ~1%|
|Endocrine||Hypothyroidism, Addison’s||Growth affected||Many chromosomal abnormalities associated with increased risk hypothyroidism|
|Traumatic||NAI, TBI||Unexplained injury, frequent ED presentations||Must always consider|
|Environmental||Abnormal postnatal nutrition, neglect||Growth affected, abnormal attachment|
|Cerebral malformations||Lissencephaly, Chiari malformation||Abnormal head circumference, seizures|
|Infections||Perinatal eg. Rubella, CMV
Postnatal eg. Meningitis
|IUGR||Mother may be asymptomatic|
|Toxins||Antenatal eg. Maternal alcohol, illicit drugs, anti-epileptics, maternal PKU
Postnatal eg. Lead
|If you don’t ask, they won’t tell|
|Neuromuscular disorders||Muscular dystrophy, myotonic dystrophy, congenital myopathy||Reduced foetal movements, feeding difficulties, hypotonia|
|Prematurity||May be in setting of prematurity alone or complications of prematurity eg. Sepsis, IVH, CNLD|
UCD = urea cycle defects NAI = non-accidental injury TBI = traumatic brain injury IVH = intraventricular haemorrhage CNLD = chronic neonatal lung disease
What are some “red flags” which should precipitate referral?
What are the components of a structured approach to a child with developmental delay?
- Physical examination
- Developmental assessment
- Targeted tests7
- Maternal history, for example recurrent spontaneous miscarriages suggesting chromosomal rearrangement/unbalanced translocation
- Previous stillbirths, neonatal deaths or sudden infant death may underlie an inborn error of metabolism
- Exposure to potential teratogens, for example anti-epileptics, antidepressants, warfarin, roaccutane, alcohol (including binge drinking in the first trimester), nicotine and illicit drugs
- Early neonatal events: complications of delivery, hypotonia, hypoglycaemia and/or seizures
- Family history, for example parental consanguinity, history of neurological disorders, learning or developmental problems
- Sleep disturbance and nocturnal snoring
- Diet and pica
- General medical history.
- Growth parameters
- Neurocutaneous stigmata
- Features of storage disorders, eg. Organomegaly, corneal clouding
- Visual examination
- Neurological signs
- Hearing assessment 10
What investigations should be done in the assessment of developmental delay?
Genetic studies: cytogenetics and fragile x should be considered on a screening basis
Neuro-imaging: wide variation in yield (9 – 80%; yield increased based on pre-test probability e.g. Abnormalities of head size, presence of seizures). Both MRI and high-resolution CT have been used with the clinician needing to weigh up the differences in radiation exposure, availability and need for general anaesthetic when selecting modality.
The bottom line
- Global developmental delay is common, with a broad aetiology – in many cases, no cause may be established
- Establishing the cause may be therapeutic, not only for the affected child but also their family
- Investigations should be selective and guided by thorough a history and examination
- Developmental assessment is not done as a “one-off” but rather ongoing assessment of the child’s trajectory
1 Royal Australian College of Physicians. 2013 August. Early Intervention for Children with Developmental Disabilities. Link:
2 National Disability Insurance Agency. Australian Department of Human Services. Access to the NDIS – Early Intervention Requirements. Link:
3 Bradley W, Daroff R, Fenichel G et al. Neurology in Clinical Practice: Principals of Diagnosis and Management (Version 4). Philadelphia. Elsevier, 2004.pp75 – 81.
4 Pivalizza P, Lalani S. 2018 July 19. Intellectual disability in children: Definition, diagnosis, and assessment of needs. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA.
5 Bélanger S, Caron J. Evaluation of the child with global developmental delay and intellectual disability, Paediatrics & Child Health, 23(6), 16 August 2018, Pages 403–410, https://doi.org/10.1093/pch/pxy093
6 Shevell M, Ashwal S, Donley D et al. Practice parameter: evaluation of the child with global developmental delay: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society. Neurology 2003; 60: 367–80.
7 Horridge K. Assessment and investigation of the child with disordered development. Archives Diseases in Childhood. Education and Practice Edition. 2011 Feb; 96: 9–20
8 Walters, V. A. Developmental Delay Causes and Investigation. Advances in Clinical Neuroscience and Rehabilitation, 2010, 10(2): 32- 34
9 Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice (Red Book) – ‘Red flag’ early intervention referral guide. 9th Edition. 2016. Appendix 3A.
10 Silove N, Collins F, Ellaway C. Update on the investigation of children with delayed development. Journal of Paediatrics and Child Health. 2013 July. 49 (7): 519 – 525
11 McDonald L, Rennie A, Tolmie J et al. Investigation of Global Developmental Delay. Archives of Diseases in Childhood. 2006 August. 91 (8): 701 – 705