Genetics Flashcards
what are Qualities of a good counsellor
- Respect and establish trust
- Confidentiality
- Patient autonomy / non-directiveness
- Empathic
- Non-judgmental attitude
- Patient advocate
- Individualization
- Sensitivity to language and cultural differences
- Role of health professional: ‘supportive’, ‘enabler
what are Clinical signs of down syndrome
- Short palpebral fissures
- Small nose
- Flattened face
- Smooth philtrum
- Thin upper lip
- Upward slanting eyes
- small eyes
- short neck
- One crease in the palm of their hand (palmar crease).
they are at risk of leukaemia and alzhemiers when older
what are other features of Down syndrome
- Poor/weak muscle tone
- Impaired intellectual ability
- Heart defects
name screening tests for Down syndrome
Ultrasound
Maternal serum screening
non-invasive parinatal screening(NIPS/NIPT)
WHEN Can you use each of the screening tools for Down syndrome
Ultrasound in first trimester: nuchal translucency scan 11-13weeks. Increased NT
detects 75% T21 cases.
- Maternal serum screening: 15-18 weeks, triple test (AFP, BhCG, oestradiol), 60%
T21
- Ultrasound in second trimester: 18-23 weeks, FA scan
- Non-invasive perinatal screening (NIPS/NIPT): >10 weeks, cell free DNA in
maternal blood, most accurate for T21
what are the SCREENING tests for Down syndrome
Ultrasound in first trimester: nuchal translucency scan 11-13weeks. Increased NT
detects 75% T21 cases.
- Maternal serum screening: 15-18 weeks, triple test (AFP, BhCG, oestradiol), 60%
T21
- Ultrasound in second trimester: 18-23 weeks, FA scan
- Non-invasive perinatal screening (NIPS/NIPT): >10 weeks, cell free DNA in
maternal blood, most accurate for T21
what can you look at for diagnosing Down syndrome
karyotype and QF-PCR
Why a couple might battle to decide whether to have testing done or not
- Risks associated with screening
- Religious beliefs
- Denial
- Differing opinions
Which medications are contraindicated in pregnancy
Roaccutane
Warfarin
Carbamazepine
what are teratogenic factors
o Medications - Drug categories
o Contraindicated
Roaccutane
Warfarin
Carbamazepine
o Infections
TORCH
o Maternal illness
Uncontrolled diabetes
what happens in FDA category C
Risk cannot be ruled out, potential benefits may justify potential risk
what happens in FDA category A
no risk is shown in the drug
what happens in FDA category X
the drug is contraindicated in pregnancy
what are indications for genetic counselling
Prenatal risk for Down syndrome: AMA or other screening
Ultrasound identified abnormalities
Family History of genetic condition – e.g. cystic fibrosis
Previous abnormality – e.g. child with Down syndrome
Exposure to teratogens
o Medications - Drug categories
o Contraindicated
Roaccutane
Warfarin
Carbamazepine
o Infections
TORCH
o Maternal illness
Uncontrolled diabetes
Consanguinity
Increased risk of recessive conditions
what is the deal with advanced maternal age and which age group is that
women above the age of 35
o The risk of chromosomal abnormalities of a fetus increases with increasing age of the
mother.
o Older women have a greater chance of underlying disease that may increase the risk
of congenital abnormalities in their offspring, e.g. Diabetes Mellitus
Ultrasound in second trimester - Fetal anomaly (FA) scan (18 to 23 weeks
o Soft markers, e.g.
o Echogenic bowel
o Short femur
o Short humerus
o Nuchal fold more than 6mm
o Hypoplastic nasal bone
o Hydronephrosis
o Major abnormalities e.g.
cardiac defects
Neural tube defects
Maternal serum screening
o 15-18 weeks
o “triple test”- AFP, BhCG, Oestradiol
o T21 - 60% <35 / 75-90% >35 T18 - 60 –75%)
o 4 in 1 test- adds dimeric inhibin A (increases detection +- 10%)
o Increased AFP – useful in detection of open NTD’s
o Not offered in the state system
Ultrasound in first trimester
o Nuchal Translucency scan:
o 11 – 13 weeks
o Increased NT - Detects up to 75% Down syndrome
o Combined with and BhCG PAPP-A (85% )
o Combined with presence/absence of nasal bone (95%)
o New U/S markers being added
o (5% false +)
o Major abnormalities (e.g. anencephaly)
SCREENING TESTS VS DIAGNOSTIC TESTS
Screening tests are non-invasive and are used for prenatal screening. Only give us an
indication as to how likely it is that the fetus has a specific condition. Screening tests can
identify cases that may benefit from diagnostic testing. Diagnostic tests can provide a clear
diagnosis, but are associated with a risk of miscarriage.
DIAGNOSTIC TESTS
Foetal karyotype obtained by:
o Chorionic villus sampling (CVS)
11-13 weeks
1-2% risk of miscarriage
Results: 2-3 weeks
o Amniocentesis
16-20 weeks
1 in 500 risk of miscarriage
Results: 72 hours or 3 weeks depending on test
o Cordocentesis
After 20 weeks
2% risk of miscarriage
Results: 3 days
Karyotype
o Results takes 2 to 3 weeks
o Cells are cultured
o Full karyotype
o Provide information on numerical and structural abnormalities of all chromosomes
o Indicated when multiple abnormalities are detected on ultrasound
QF-PCR
o Result within 72 hours
o No culture required
o Also only give info about possible trisomy 13,18, 21 and sex chromosomes
o Can’t distinguish between trisomy and translocations
o Indicated when one of the above trisomies are suspected
FISH (Fluorescent In Situ Hybridization)
o can be requested for quick result (2-3 days)
o Will only give info about possible trisomy 13,18, 21 and sex chromosomes.
o Not full karyotype
o Indicated when one of the above trisomies are suspected
TOP ACT - CHOICE ON TERMINATION OF PREGNANCY ACT, 1996 (ACT NO. 92, 1996.)
- First 12 weeks – upon request
- 13-20 weeks – a medical practitioner in consultation with the woman finds a :
– Risk of injury to the physical or mental health of the woman
– Substantial risk of severe physical or mental abnormality to the fetus
– Rape or incest
– Significant effect to the social or economic circumstances of the woman - After 20 weeks - a medical practitioner, after consultation with another medical practitioner
or a registered midwife, finds that the pregnancy will:
– Endanger the woman’s life
– Result in severe malformation of the fetus
– Pose risk of injury to the fetus
Doctor/ genetic counsellor should provide:
o Non-directive genetic counselling on abnormal results
o Diagnosis and prognosis for the fetus
o Discussion of options related to pregnancy
* TOP (TOP act*)
* TOP for Down syndrome allowed up to 24 weeks
o Full implications of all choices
o Time for decision-making
o Supportive counseling
The doctor/ genetic counsellor, at all times, must
o Maintain a non-judgmental attitude
o Accept the policy of freedom of choice
o Believe in the rights and worth of the individual
o Believe that people choose what is right for them in their situation, and according to
their values and beliefs
o Provide individualized counselling
Grief response
o Denial, anger, bargaining, depression, acceptance
o Search for cause.
o Guilt
o May be couple differences in reaction to diagnosis
Breaking bad news (After Robert Buckman’s six step protocol)
o Getting started
o How much does the patient know
o How much does the patient want to know
o Information sharing
o Responding to feelings
o Planning and follow-up
