Antenatal and postnatal screening

Question 1

What is the purpose of the dating scan?

Answer 1

Determines stage of pregnancy and the due date

Question 2

How many ultrasound scans do pregnant women receive and at what stage of pregnancy are they performed?

Answer 2

Two:

Dating scan - 8-14 weeks
Anomaly scan - 18-20 weeks

Question 3

what is the purpose of the anomaly scan?

Answer 3

Checks for serious physical abnormalities

Question 4

Why is timing important when deciding when to do biochemical tests on a pregnant women?

Answer 4

Could result in false positive or false negative results if tests are done at a stage in pregnancy where the level of that biochemical marker would be high/ low anyway

Question 5

What is a screening test?

Answer 5

detects signs and symptoms associated with a condition

assesses probability of the individual having a condition

NOT A DEFINITIVE TEST

Question 6

What is a diagnostic test?

Answer 6

A definitive test used to establish whether a person has a specific condition or not

Question 7

In what scenarios may a pregnant woman be offered a certain diagnostic test?

Answer 7

• evidence of potential abnormality from a screening test
• family history of genetic condition
• women is over 35

Question 8

Examples of diagnostic tests?

Answer 8

• Amniocentesis
• Chorionic villus sampling

Question 9

Explain the process of amniocentesis

Answer 9

-withdrawal of amniotic fluid containing fetal cells

• cells are cultured in order to produce a karyotype which allows for the diagnosis of multiple genetic conditions

Question 10

what is a karyotype?

Answer 10

• A visual display of a persons chromosome complement
• Allows for the diagnosis of genetic disorders

Question 11

When in a pregnancy is amniocentesis usually performed?

Answer 11

weeks 14-16

Question 12

Explain the process of chorionic villus sampling

Answer 12

• A tube is inserted into the female reproductive tract in order to sample placental cells
• These cells are cultured to produce a karyotype

Question 13

what are the advantages/ disadvantages of amniocentesis and chorionic villus sampling?

Answer 13

• chorionic villus sampling can be carried out earlier in pregnancy (as early as 8 weeks) compared to amniocentesis, therefore termination of pregnancy can be carried out earlier
• CVS is a more invasive procedure than amniocentesis with higher likelihood of miscarriage due to the procedure

Question 14

Explain what causes PKU

Answer 14

a substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non functional

A build up of phenylalanine can result in mental impairment

Question 15

How do people with PKU manage their condition?

Answer 15

diet low in phenylalanine

Question 16

How is PKU detected in newborns?

Answer 16

Blood tests are done on newborn babies to identify excess phenylalanine