Prenatal diagnosis of genetic diseases

Question 1

What are the 5 main indications for referral for prenatal testing?

Answer 1

Abnormal findings in nuchal/mid trimester scan
Results from combined test shows increased risk of Down syndrome
If previous pregnancy was affected
If parents are carriers of chromosome rearrangement/genetic condition
Family history of genetic condition

Question 2

What is the combined test for Down’s syndrome?

Answer 2

Levels of free beta-hCG and protein PAPP-A tested

Down’s babies have high hCG and low PAPP-A

Question 3

What are the 5 reproductive options available?

Answer 3

Planning prenatal testing
Facilitating decision making
Seeing patients in clinic following in utero diagnosis
Arrange termination if neccessary
Discuss recurrence risks and plans for future pregnancies

Question 4

What 6 psychosocial aspects are associated with reproductive decision making?

Answer 4

Previous experiences
Family situation
Personal beliefs
Psychosocial situation
Miscarriage risk
Genetic risk

Question 5

What 2 invasive tests are used and why?

Answer 5

Offered if there is a known risk
Looks at molecular, cytogenetic and biochemical markers
Amniocentesis
-sample amniotic fluid which contains fetal cells
Chorionic villus sampling
-samples chorionic villi which has same DNA as fetus

Question 6

What 3 non-invasive tests are used and why?

Answer 6

Maternal serum screening
-markers in blood indicate risk of trisomy 21, 18, neural tube defects
Ultrasound
cffDNA
-analyse DNA fragments in maternal plasma