Down Syndrome

Question 1

How common is down syndrome?

Answer 1

affects 1 in 800 births

Question 2

What increases the risk of having a child with down syndrome? Why?

Answer 2

The risk of having a child with down syndrome increases with maternal age. Since women are born with all their eggs, being older means a woman’s eggs have had more time to be exposed to a damaging agent.

Question 3

Generally speaking, what causes down syndrome?

Answer 3

A genetic defect.

Question 4

What are the two specific problems that cause down syndrome?

Answer 4

1) trisomy of chromosome 21 - the cause behind 95% of down syndrome
2) Robertsonian translocation

Question 5

Explain how a Robertsonian translocation can cause down syndrome.

Answer 5

A parent has a Robertsonian translocation, where a long arm on chromosome 21 is switched with an arm on chromosome 14. There is potential now that an offspring could end up with two normal chromomosome 21s as well as a chromosome 14 that is abnormal and has the long arm of chromosome 21 on it. Essentially this offspring would have three versions of the long arm of chromosome 21.

Question 6

What are some manifestations of down syndrome?

Answer 6

• decreased growth
• small head
• flat face
• slanted eyes
• open mouth and protruding tongue
• short, stubby hands with one palmar crease
• malformed ears
• big space between 1st and 2nd toe
• impaired/delayed cognition
• heart defects
• GI malformatios
• increased risk of leukemia
• increased risk of Alzheimer’s

Question 7

What prenatal screening can be done to detect down syndrome?

Answer 7

• maternal blood test to determine risk
• fetal nuchal translucency, done with ultrasonograph at 10-13 weeks gestation
• chromosome analysis (only accurate diagnosis) of chorionic villus sample, amniocentesis, percutaneous umbilical blood sample