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

dss

  • 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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