Genetics Lecture 11 - Prenatal Diagnosis

Question 1

Name the six reasons for a referral to prenatal diagnosis.

Answer 1

1. Abnormal prenatal screening
2. Advanced maternal age (35 or older)
3. Suspected fetal structural abnormalities on ultrasound
4. Previous child with chromosomal abnormality
5. Risks identified through genetic testing or counseling of parents
6. Family history of a child with a congenital abnormality or genetic disorder

Question 2

When is a dating ultrasound performed?

Answer 2

8-10 weeks

Question 3

When can a CVS be performed?

Answer 3

11-13 weeks

Question 4

When can an amniocentesis be performed?

Answer 4

15-19 weeks

Question 5

Can CVS detect neural tube defects?

Answer 5

No

Question 6

What is the miscarriage risk for amnio?

Answer 6

1/200-1/600

Question 7

What malformation has been associated with early amnio?

Answer 7

Clubfoot

Question 8

What is the miscarriage risk for CVS? What are the other risks?

Answer 8

1/100. Other risks are limb malformation, maternal infection

Question 9

What are two advantages of CVS over amnio?

Answer 9

1. Detects mosaic trisomy - a precursor to UPD

2. Performed early (11-13 weeks)