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Down Syndrome - management of the neonate

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Background

  • Down Syndrome (Trisomy 21) is the most common chromosomal abnormality, with a frequency of 1:1000 livebirths.1 
  • It is commonly diagnosed in the immediate newborn period after an apparently uneventful pregnancy. 
  • Whilst it is common to offer antenatal screening for Down Syndrome, not all women choose to undergo testing. Non-invasive screening methods (such as serum screening, nuchal skinfold thickness, nasal bone prescence and ultrasound) have a false-positive and false-negative rate when compared to direct karyotypic testing of fetal genetic material by amniocentesis or chorionic villous sampling. 
  • Despite the prevalence of structural abnormalities in Trisomy 21, many infants with undiagnosed Trisomy 21 have had fetal anatomy screens performed that have not identified any abnormality. 
  • Although there is a clear relationship between advancing maternal age and the risk of Trisomy 21, 70% of Down Syndrome infants are born to mothers below the age of 35 years.2 
  • The risk of Trisomy 21 in the general population primarily depends on maternal age. Approximate risks are:
    15-29 years  1:1500
    30-34 years  1:800
    35-39 years   1:270
    40-44 years   1:100
    > 44 years  1:50
  • Approximately 94% of Down Syndrome cases will have "classic" Trisomy 21 with a complete copy of an additional chromosome 21. 
  • The remaining 6% will have mosaicism or an unbalanced translocation (usually between chromosomes 14 and 21). 

Assessment in the Neonatal Period

  • Diagnosis in the newborn period is a very challenging time for parents and for staff. Often the celebration of the birth of the baby is dampened by the realisation that the infant has a major chromosomal abnormality with significant developmental and health implications.
  • The parental response is often one of distress, with a period of anger and/or grief before there is acceptance of the diagnosis.
  • All infants - whether diagnosed antenatally or postnatally - should be seen by a neonatal specialist.
  • Discussion with the parents should be held in a private place with both parents present. The parents should be given the time they need to absorb the news. Repeat visits may be necessary to deal with questions and distress.
  • Information pamphlets and other reading material are available from the Family Liaison Nurse in NICU.
  • Routine assessment by the genetics service is not required unless there is doubt about the clinical diagnosis or there are other unusual features. Referral to genetic service is recommended for discussion of recurrence risk, particularly if the trisomy is due to a chromosome translocation or if other chromosomal abnormalities are found on karyotype examination.

Investigations

Karyotype 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.
Cardiac assessment
Chest radiograph
ECG
Referral to Paediatric Cardiology
Approximately 40% of infants will have congenital cardiac disease.
The most common lesions are endocardial cushion defects, ventricular septal defects, patent ductus arteriosus, and atrial septal defects.
Full blood count Haematological problems are common in Down Syndrome.3
Thrombocytopenia (<100) occurs in up to 28% of infants. The thrombocytopenia is usually mild (>40) and transient (2-3 weeks).
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 congenital hypothyroidism.
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.

Referrals

Parents should be aware of which referrals have been made.

Referral to paediatrician

Central Auckland  Developmental paediatrics (Starship).
Paediatricians from this service will often meet with the family prior to discharge.
The specialist or registrar/NSANP should contact the team support administrator (Ext.22489), and complete a written referral (please fax to Ext.22483).
North Shore  General Paediatrics, North Shore Hospital.
West Auckland (west of Avondale)  General Paediatrics, Waitakere Hospital (West Kids).
South Auckland (east of Panmure, south of Otahuhu) General Paediatrics, Middlemore (KidzFirst).
Elsewhere in New Zealand Local general paediatric service.

Visiting neurodevelopmental therapist

Note that this is different to the developmental paediatric service. A separate referral (available via the intranet only) needs to be sent.

  • Central Auckland - Central Auckland CDS.
  •  North Shore - North Shore and Rodney Child CDS.
  • West Auckland - Waitakere CDS.
  • South Auckland - South Auckland CDS.
  •  Elsewhere in New Zealand May be appropriate to ask the local paediatric service to organise referral.

Social worker

  • Can provide parents with appropriate forms for the Child Disability Allowance and other community based support services.
  • Will be able to assist with counselling and other support.

Speech language therapy or lactation consultant, as appropriate.

Infants with Down Syndrome often feed poorly initially and this is frequently the process that determines when the baby will be ready to be discharged.

Audiology (out-patient)

  • Hearing impairment occurs in up to 75% of individuals.
  • A referral should be sent for audiology assessment.

Ophthalmology clinic, Green Lane Clinical Centre.

Cataracts, strabismus, and refractory errors are common. Refer to the ophthalmology service at Green Lane Clinical Centre.

General Practitioner

The GP should be informed that the baby has Down Syndrome, whether significant congenital cardiac disease or other conditions are present, and what follow-up is planned.

Support for parents

  • Information is available from the Nurse Specialist - Family Liason in NICU.
  • Provision of the specific Down Syndrome information pack should be withheld until either
    The karyotype is confirmed, or
    The parents request the information themselves, or
    The paediatrician looking after the baby feels that it would be appropriate.
  • Parents should be given information about the supports and services the New Zealand Down Syndrome Association (http://nzdsa.org.nz/) can provide to parents and individuals with Down Syndrome.
    Phone 0800 NZDSAI (0800 693724)
    Email: national.coordinator@nzdsa.org.nz

Other issues

Genetic counselling

It may be appropriate to discuss recurrence risk in the newborn period.

  • For mothers who have had an infant with "classic" Down Syndrome, the generally quoted recurrence risk is 1% (but is higher if maternal age is greater than 40). The recurrence risk for mosaic Down Syndrome is 1-2%.
  • For an unbalanced translocation, then recurrence risk will depend on whether one of the parents has a balanced translocation. The recurrence risk if the mother is a carrier is 12%, and 1% if the father is a carrier.

Other neonatal health issues

  • Other structural abnormalities that may present in the perinatal period include duodenal atresia, oesophageal atresia, tracheal stenosis, pyloric stenosis, anorectal anomalies, and Hirshsprung's Disease.
  • Persistent pulmonary hypertension is more common in the newborn period, even in the absence of congenital cardiac disease.
  • Prophylaxis for bacterial endocarditis will depend on underlying cardiac conditions.
  • Airway obstruction is rare in the newborn period but may develop in early childhood.
  • Atlanto-axial instability, which occurs in up to 20% of individuals with Down Syndrome, is not usually a significant issue in the newborn period.

References

  1. The clinical assessment and management of children, young people and adults with Down Syndrome: recommended clinical practice: New Zealand Ministry of Health, 2001.
  2. 2 Rosen T, D'Alton ME. Down Syndrome screening in the first and second trimesters: what do the data show? Semin Perinatol 2005;29:367-75.
  3. 3 Christensen RD. Hematological problems in the neonate. 1st ed. Phil: W.B. Saunders Co, 2000.

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Document Control

  • Date last published: 25 September 2018
  • Document type: Clinical Guideline
  • Services responsible: Neonatology
  • Owner: Newborn Services Clinical Practice Committee
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years