NEONATAL CONDITIONS
Trisomy 21 (Down Syndrome)
A practical guide for SCN clinical staff · The commonest chromosomal disorder - recognising the associations and supporting families
THE
ASSOCIATIONS
Trisomy 21
An extra copy of chromosome 21: ~95% free trisomy from meiotic nondisjunction (the risk rises with maternal age), ~4% translocation (may be inherited - check parental karyotypes), ~1% mosaic.
Gene-dosage effect
A third copy raises expression of chromosome 21 genes; it is this dosage imbalance across many genes - not a single gene - that drives the multisystem phenotype and its variability.
Cardiac (~40-50%)
AVSD is the most characteristic lesion - arrange an echocardiogram for every baby, even without a murmur.
Gastrointestinal
Duodenal atresia ("double bubble"), Hirschsprung disease, anorectal malformation and TOF.
Haematological
Transient abnormal myelopoiesis, polycythaemia, and a higher later risk of leukaemia.
Endocrine
Congenital and acquired hypothyroidism - screen and follow up.
Other systems
Hearing and vision, atlantoaxial instability, feeding difficulty and later obstructive sleep apnoea.
CLINICAL FINDINGS
- Hypotonia and excess nuchal skin
- Flat facial profile, upslanting palpebral fissures, epicanthic folds, Brushfield spots
- Single palmar crease, sandal gap, brachydactyly or clinodactyly
- Small ears, flat occiput
- Features vary - none is diagnostic on its own
INVESTIGATIONS
- Karyotype to confirm and define translocation vs trisomy (recurrence counselling)
- Echocardiography for every baby, regardless of a murmur
- FBC and film (transient abnormal myelopoiesis, polycythaemia), TFTs
- Feeding/swallow assessment; investigate for GI obstruction if symptomatic
- Hearing screen, red reflex and ophthalmology review
COMPLICATIONS & RED FLAGS
- Duodenal atresia: bilious vomiting and a double bubble - surgical
- Critical congenital heart disease - screen even if asymptomatic
- Transient abnormal myelopoiesis can progress or infiltrate organs - involve haematology
- Feeding difficulty and poor weight gain
- Deliver the diagnosis sensitively - the first conversations matter
MANAGEMENT
Share the news sensitively and screen the associations - an echocardiogram for every baby, plus GI, haematological, thyroid, hearing and vision review.
At birth / diagnosis
- Examine for dysmorphic features and anomalies; confirm with a karyotype
- Share the news sensitively, ideally with both parents together, using respectful, balanced language
- Provide written information and support contacts (e.g. Down Syndrome Australia)
- Avoid assumptions about prognosis
Screen associations
- Echocardiogram for every baby
- FBC and film, TFTs, red reflex, hearing screen
- Assess feeding; investigate GI obstruction if vomiting or not passing meconium
- Document and arrange follow-up of each system
Support & follow-up
- Multidisciplinary follow-up (paediatrics, cardiology, early intervention)
- Support breastfeeding and allow extra time for feeds
- Connect the family with peer support and services
- Use the national health-checklist schedule for ongoing surveillance
- Use respectful, person-centred language ("baby with Down syndrome") and support parents through the first conversations without assumptions.
- Support feeding - babies with hypotonia may tire and need extra time, positioning, or expressed breast milk.
- Watch for bilious vomiting, failure to pass meconium, or cardiac and respiratory signs and escalate.
- Help connect families with written information and peer support, and involve them in care.
How do you deliver a new diagnosis of Down syndrome sensitively to parents?
Why does every baby need an echocardiogram, even without a murmur?
Which gastrointestinal and haematological associations must you actively look for?
Why does the type of chromosomal abnormality matter for the family?
Take-home message: Trisomy 21 is the commonest chromosomal disorder, often suspected antenatally and confirmed by karyotype. The newborn priorities are to share the diagnosis sensitively and to screen the associations - an echocardiogram for every baby, plus GI, haematological, thyroid, hearing and vision review. With coordinated multidisciplinary care and family support, most babies do well.
For educational purposes only. Always align management to current ANZCOR/NRP guidelines and your local SCN/NICU or NETS protocols.