Contents
Introduction
Edwards syndrome is a genetic disorder caused but he presence of an additional (3rd ) copy of chromosome 18. The condition results from problems with cell division during early development of the foetus. It is one of the conditions that is screened for as part of the first trimester screening test.
Edwards syndrome is the second most common trisomy after Down Syndrome (trisomy 21).
Edwards syndrome results in multiple abnormalities including a small head, clenched fists with overlapping fingers and severe intellectual disability. Occasionally (about 6% of cases) only a proportion of the cells int he body are affected with the extra chromosome (mosaicism) which causes a milder form of the disease.
Edwards Syndrome occurs in about 1 in 6,000 live births. Most affected babies die before birth, but 5-10% will survive beyond one year of age.
Edwards syndrome is named after English geneticist John Hilton Edwards.
Epidemiology & Aetiology
- Affects 1 in 6,000 live births
- Risk is increased if there is a family history
- Risk increases with advancing maternal age
- Chance of a second baby with Edwards Syndrome for an affected family is about 1%
- Live born infants with Edwards Syndrome are more likely to be female
Presentation
- Most cases in the developed world are diagnosed in first trimester screening
- In this circumstance – about 85% of parents choose termination
- After a first trimester screening test with a high probability of Edwards Syndrome then amniocentesis or chorionic villus sampling should be offered to confirm the diagnosis
- There are specific ultrasound findings that are characterise of Edwards Syndrome that can be seen during first trimester screening of the foetus. These include:
- Growth restriction
- single umbilical artery
- Polyhydramnios – excess amniotic fluid
- Strawberry shaped head
- Overlapping fingers
- Congenital heart defects (>90% of cases)
- Live born infants with Edwards Syndrome may suffer from:
- Congenital heart defects
- Gastrointestinal abnormalities
- Severe gastro-oesophageal reflux often leads to aspiration and is a common cause of death
- Intra-abdominal tumours – such as Wilm’s tumour are common
- Severe intellectual disability
- Seizures
- Structural eye defects
Parents will need extensive and realistic counselling about the likely outcome of proceeding with a pregnancy and what the quality of life will entail for their child.
In addition – genetic screening of the parents should be offered – as some cases may be due to an unbalanced translocation which can occur in future pregnancies.
Management and prognosis
Pre-term delivery is common, and up to 40% of babies that progress to delivery will die during delivery.
- Median survival for live births is just 14 days
- Survival to 3 months is 20% and to 1 year is 5-10%
- For those with trisomy 18 mosaicism survival to one year is 70%
Feeding issues are common and tube feeding may be required.
Causes of death are usually a combination of cardiac failure, respiratory failure, aspiration and upper airway obstruction.
Management generally depends on the individual specific abnormalities. Quality of life for affected babies is generally poor. Treatment is generally only supportive and typically life-prolonging measures are not often encouraged. However, there is considerable ethical debate around this and some studies have shown 1-year survival as high as 25% when full resuscitation and intensive care are offered.
References
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
- Edwards’ Syndrome – patient.info