- To confirm the clinical diagnosis and to provide information
that will help with counselling.
- In most instances, a standard karyotype will be analysed
within 5 days.
- An urgent FISH specifically for Trisomy 21 is indicated only
in exceptional circumstances.
- Chest radiograph
- Referral to Paediatric
- Approximately 40% of infants will have congenital cardiac
- The most common lesions are endocardial cushion defects,
ventricular septal defects, patent ductus arteriosus, and atrial
Full blood count
- Haematological problems are common in Down Syndrome.
- Thrombocytopenia (<100) occurs in up to 28% of infants. The
thrombocytopenia is usually mild (>40) and transient (2-3
- Polycythaemia is common.
- Transient myeloproliferative disorders (leukaemoid
reactions) may occur in the newborn period. Infants with Trisomy
21 are 10-20x more likely to develop leukaemia.
Thyroid function tests
Newborn Metabolic Screening card is sufficient.
- Approximately 1% of infants with Down Syndrome will have
- If the infant has clinical signs suspicious of
hypothyroidism (for example,
prolonged jaundice), a T4
and TSH should be requested.
- 15% of Down Syndrome individuals will develop hypothyroidism.