2.3 Ante- And Postnatal Screening

Question 1

What is the purpose of antenatal screening

Answer 1

To identify the risk of a disorder so that further tests and a prenatal diagnosis may be offered.

Question 2

What are the two types of antenatal screening test

Answer 2

Ultrasound imagining and biochemical tests

Question 3

What happens in ultrasound imaging

Answer 3

An ultrasound scanner is help up against a pregnant woman’s abdomen and picks up high frequency sounds and converts them to a ultrasound image

Question 4

What are the two types of ultra sound scans

Answer 4

Dating scan and anomaly scan

Question 5

When can a dating scan be offered

Answer 5

8-14 weeks

Question 6

When can an anomaly scan be offered

Answer 6

18 - 21 weeks

Question 7

What does a dating scan do

Answer 7

Determines the stage of the pregnancy and calculates the date when the baby is due

Question 8

What abnormalities can be detected in a dating scan

Answer 8

Neural tube defects such as spina bifida

Question 9

How can Down’s syndrome be screened for in a dating scan

Answer 9

Combined with a blood test and measuring of the the fluid at the back of the baby’s neck

Question 10

What does an anomaly scan allow

Answer 10

Checks to be made for the presence of any physical abnormalities e.g. a clefts lip

Question 11

What can changes be detected by

Answer 11

Biochemical tests

Question 12

How are some medical conditions identified

Answer 12

By the presence of certain marker chemicals in the blood and urine.

Question 13

What do high levels of HCG show

Answer 13

That a foetus has Down’s syndrome

Question 14

To monitor the health of the mother and the foetus what tests should be taken

Answer 14

Alpha fetoprotein, renal/liver function, thyroid function

Question 15

Why would a false positive result

Answer 15

If a marker chemical was measured at the wrong time - could diagnose a child with condition it doesn’t have

Question 16

Why would a false negative result

Answer 16

Suggests a foetus doesn’t have a condition when it does - so time chosen for biochemical tests has to be closely synchronised with data from ultrasound scans

Question 17

What is a diagnostic test

Answer 17

A definitive test which shows whether a developing foetus actually has the condition.

Question 18

Why would diagnostic tests be offered

Answer 18

Family history of genetic disorders, of the woman belongs to a high risk category or if there is evidence of a potential problem

Question 19

What is a karyotype

Answer 19

A visual representation of an individuals chromosome complement displaying number of chromosomes, arrangement, size and structure for analysis.

Question 20

What are the two types of diagnostic test

Answer 20

Amniocentesis and chorionic villus sampling

Question 21

What is Down’s syndrome caused by

Answer 21

An extra chromosome 21 in EACH CELL

Question 22

What does amniocentesis do

Answer 22

Access whether an unborn baby could develop or is developing a serious genetic condition

Question 23

When is amniocentesis carried out

Answer 23

Weeks 14 - 16

Question 24

Describe the process of amniocentesis

Answer 24

The removing of amniotic fluid which surround the foetus. This fluid has foetal cells then collected from it, cultured and then examined under a microscope

Question 25

What are advantages of amniocentesis

Answer 25

Prenatal diagnosis possible and defects neural tube defects

Question 26

What are disadvantages of amniocentesis

Answer 26

Gives results later in pregnancy and small risk of miscarriage

Question 27

What is chorionic villus sampling

Answer 27

A second diagnostic test offered to check for genetic disorders

Question 28

Describe the process of chorionic villus sampling

Answer 28

Removal of a small sample of cells from an area of the placenta called chorionic villi. Carried out under guidance of ultrasound scanner so nothing enters amniotic fluid or touches the baby. The sample of cells are then cultured, stained and a karyotype is produced.

Question 29

What are advantages of chorionic villus sampling

Answer 29

Gives results earlier in pregnancy and prenatal diagnosis possible

Question 30

What are disadvantages of chorionic villus sampling

Answer 30

Higher risk of miscarriage and doesn't detect neural tube defects

Question 31

When does chorionic villus sampling happen

Answer 31

11 - 14 weeks

Question 32

What are the four types of blood groups

Answer 32

A, B, AB, and O

Question 33

What does your blood contain

Answer 33

Antigens and antibodies

Question 34

What antigens do each of the blood groups have

Answer 34

A - a antigens B - b antigens AB - a & b antigens O - no a or b antigens

Question 35

What antibodies do each of the blood groups have

Answer 35

A- b antibodies B - a antibodies AB - no a or b antibodies O - a & b antibodies

Question 36

What blood group is the universal donor

Answer 36

O

Question 37

What blood group is the universal recipient

Answer 37

AB

Question 38

In what situation of birth would there be a serious problem with blood

Answer 38

If a rhesus negative mother has a rhesus positive child and at birth the child's blood comes into contact with the mothers immune system.

Question 39

What is the next problem

Answer 39

If the rhesus negative mother has a second rhesus positive child

Question 40

What is postnatal tests

Answer 40

Screening tests offered to new born babies

Question 41

When do postnatal tests occur

Answer 41

First 6 - 8 weeks

Question 42

What are some postnatal screening tests

Answer 42

Physical examination, hearing screening test, blood spot (heel prick) test

Question 43

What are the benefits of postnatal screening

Answer 43

Early treatment can improve their health and prevent severe disability or death

Question 44

What is an example of a metabolic disorder

Answer 44

PKU

Question 45

What is PKU

Answer 45

An inborn error of metabolism

Question 46

What does having PKU mean

Answer 46

The body cannot turn food into energy

Question 47

What is PKU caused by

Answer 47

A genetic mutation in the PAH gene (because enzymes are proteins)

Question 48

What happens as a result of PKU in babies

Answer 48

They can't break down the amino acid phenylalanine which builds up in the blood and brain

Question 49

What is the treatment for PKU

Answer 49

A restricted diet containing minimum quantity of phenylalanine

Question 50

What is a consequence of untreated PKU

Answer 50

Mental deficiency

Question 51

What does genetic counselling involve

Answer 51

Gathering information about the occurrence of genetic conditions from an individuals family members

Question 52

What does genetic counselling provide

Answer 52

Support, information and advice

Question 53

What are all the chromosomes called (excluding sex chromosomes)

Answer 53

Autosomes

Question 54

Why may genetic counselling be carried out

Answer 54

Diagnosing a person with a genetic condition, working out the risk of someone developing a condition or determining whether someone is a carrier of a genetic condition

Question 55

Why are family tress only expected to work out the RISK of inheriting a genetic condition

Answer 55

Fertilisation is a random process

Question 56

What are the patterns of inheritance

Answer 56

Autosomal recessive, autosomal dominant, incomplete dominance and sex linked recessive

Question 57

What is an example of autosomal recessive inheritance

Answer 57

Cystic fibrosis

Question 58

What are the features of a autosomal recessive pedigree chart

Answer 58

Trait is expressed very rarely, it skips generations, expressed in some offspring of marriage between cousins and males and females equally affected

Question 59

What is an example of autosomal dominant inheritance

Answer 59

Huntington's chorea

Question 60

What are the features of an autosomal dominant inheritance

Answer 60

Trait appears in every generation, each sufferer has an affected parent, doesn't skip generations, males and females affected equally

Question 61

What is an example of autosomal incomplete dominance

Answer 61

Sickle cell trait

Question 62

What are features of autosomal incomplete inheritance

Answer 62

The fully expressed form occurs rarely, partly expressed form occurs frequently, males and females affected equally

Question 63

What is an example of sex linked recessive inheritance

Answer 63

Male pattern baldness