Genetics in obstetric care Flashcards
Reasons for referral to genetics
FH
diagnosis of genetic conditions
genetic counselling
management
7 things people need to know before undergoing a genetic test
what it is for likely to be +ve? what if it is +ve? What if it is -ve? false positives and negatives implications on family members DNA stored
the 2 types of pregnancy screening/testing are
targeted
whole population
Reproductive choices for testing
CVS amniocentesis pre implantation genetics nothing/test at birth adoption gamete donation non invasive prenatal diagnosis
x linked recessive trait with carrier mother and example
1 affected son, 1 carrier daughter and 2 unaffected
duchennes
autosomal dominant trait with 1 parent affected
50% chance
no skipped generations
Autosomal recessive with both parent carriers and example
1 normal, 2 carriers and 1 affected
sickle cell
screening for down’s syndrome
maternal age free fetal DNA triple screening - AFP, hCG and uE3 CUBS amniocentesis
list some common recessive disorders
CF, sickle cell, Tay Sachs, thalassaemia, BRCA1
Diagnosis of CF
immunoreactive trypsin - 6 weeks
sweat test and genotype
Sickling symptoms
pain - cold - dehydration - leg ulcers - eyes - kidneys - jaundice - infections - anaesthetic issues - stroke
Tay sachs - what is it?
progressive genetic lysosomal storage disease
hex A deficiency - build up of lipids in nerve cells in brain
Prognosis for Tay sachs
progressive from 6 months - fatal at 3-5 years
carriers in Ashkenazi jews and general population
jews - 1 in 25
general - 1 in 250
3 parts of newborn screening
clinical exam
hearing
blood spot - 3 to 5 days
3 reasons why we screen babies
- early detection of pre-symptomatic
- early treatment
- reduce anxiety over symptoms
What do we screen babies for?
PKU, CHT, CF, sickle cell
MCADD, homocysteinuria, maple syrup urine disease
PKU inheritance
recessive
PKU - what is it?
unable to break down the amino acid phenylalanine
What happens to baby in PKU?
serious irreversible mental disability if not treated
Treatment of PKU
start within 21 days - diet
How much of CHT is inherited?
1 in 10 cases
Treating CHT
thyroxine tablets by day 21
inheritance of MCADD
recessive
MCADD
cannot easily breakdown fat so if skip meals can be life threatening
age of presentation and mortality in MCADD
14 months - 25%
Treating MCADD
avoid fasting and have frequent meals
emergency - glucose polymer and IV dextrose
Pros and cons of next generation sequencing
costs fall and quicker to interpret data
still need scientists, variant interpretation takes time and still need to confirm result
