Downs Syndrome

Background/Epidemiology

• Down syndrome is the most common chromosomal disorder (trisomy 21- often detected by QF-PCR) in humans.
  • Prevalence ~1 in 650-1000 pregnancies

Risk Factors

• It has been shown that the risk of Down’s syndrome exponentially increases with the age of the mother
  • beginning at around age 35 (1:385); 40 (1:106) and 45 (1:30)

Screening

• During pregnancy, all mothers are offered screening for Down’s syndrome
  • This is an optional screening test
•  Screening tests include
  • Nuchal Translucency at the booking scan (ideally after 11+2 weeks for accuracy)
    • NB This is routine for all pregnancies as this can be a sign of multiple abnormalities (not just Down’s syndrome) e.g. heart defects
  • PAPP-A and hCG can also be taken at this time (maternal blood test)
  • AFP, oestrodiol and inhibin can be taken at 15-20 weeks (maternal blood test)
• Screening tests are used to calculate the risk

• Patients will then be offered definitive tests
  • Amniocentesis (>15 weeks)
  • Chorionic villous sampling (>12 weeks)

Continuing/Termination of Pregnancy

• If the mother chooses to continue the pregnancy, antenatal care will continue.  The abnormality scan at 20-24 weeks will try to pick up any major/serious abnormalities e.g. heart defects etc and the pregnancy may require closer follow-up from then on, and possibly require early induction.
• If the mother chooses to terminate the pregnancy, she may do so
  • In the legal abortion forms, this would be justified as a risk to the mother’s mental health

Features of Down’s syndrome

• Neonatal features to examine for post-natally
  • General
    • Hyperflexibility; muscular hypotonia
    • They may be small/low birth weight than expected
    • May generally have trouble feeding (reflux)
  • Head
    • Small head (brachycephaly)
    • Slanted eyes (oblique palpebral fissures)
    • Epicanthic folds (eyelid folds)
    • Brushfield spots (brown/grey spots on the edge of the iris)
    • Low set ears, which may be folded
    • Flat nasal bridge
  • Mouth
    • Protruding tongue (small narrow palate)
    • High arched palate
  • Neck
    • Loose skin around the nape of the neck
  • Hands
    • Single palmar crease
    • Short little finger
    • In-curved little finger
    • Short broad hands
  • Feet
    • Gap between hallux and second toes
• Systemic features
  • ~50% will have a congenital heart defect
    • 9/10 septal; less commonly (but more serious), tetralogy of fallot and patent ductus arteriosus
    • 60% require active management
    • Babies with down’s syndrome should be assessed by Echocardiogram soon after birth to avoid delay in management
  • Gastrointestinal features are common
    • Most common are constipation, diarrhoea or indigestion (reflux and vomiting)
    • However, babies with Down’s are also at a higher risk of oesophageal and duodenal atresia
      • Former can be associated with tracheo-oesophageal fistula and can result in serious pneumonia as well as failure to thrive
      • Latter can result in obstruction requiring surgery
  • Around 50% of babies have problems with their hearing (commonly glue ear) and 50% will have problems with their eyesight (variety of problems e.g. squint, myopia/hypermetropia, cataracts, infections etc)
  • Other problems include hypothyroidism (10%) and myelodysplasia (increasing the risk of infections- particularly pneumonia; as well as acute leukaemia (1 in 100)
  • Dementia
    • IMPORTANT- whilst people with Down’s syndrome develop dementia earlier (e.g. 30-40); there is no evidence to suggests that they are at more risk than the general population

Development

• People with Down’s syndrome tend to be late at reaching developmental milestones and learning disabilities.
• Most areas now have early access to speech/language, physiotherapy, education specialists and the correct support for learning in schools to support children with Down’s syndrome

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