Prenatal Diagnosis of Genetic Diseases Flashcards
What is taken into account at a scan?
maternal age, hormone levels, nuchal translucency and thickness, nasal bone, fatal heart blood flow, abnormalities
What is nuchal translucency and what does it indicate?
thickness of fluid at back fo the neck
if over 3mm then can indicate chromosomal abnormalities, birth defects, skeletal dysplasia
What is used as an indication for prenatal testing?
abnormal findings at nuchal or mid trimester scan
results of test show increased downs risk
previous pregnancy with condition
parents are a carrier of chromosome rearrangement or genetic condition
What are the prenatal tests available?
scanning, invasive and non-invasive
What is maternal serum screening?
non-invasive test for maternal serum markers in blood to detect increased risk of trisomy 21/18 and neural tube defects
What is cell-free foetal DNA? What does it test for?
non-invasive
analyse DNA fragments present in maternal plasma as 15% from placenta
test for achondroplasia, than atrophic dysplasia, part syndrome, X-linked condition
What is the limitation of non-invasive?
if multiple pregnancies can’t distinguish between foetus DNA
if mother has high BMI then proportion of cffDNA decrease
invasive test may still be required
What is the benefit of non-invasive?
less invasive tests, no miscarriage risk, less expertise required, earlier result
What is chronic virus sampling? risk?
a sample of chorionic villi is taken to get foetla DNA via trans abdominal or vaginal
risk of miscarriage (1-2%)
What is amniocentesis? Risks?
samples of amniotic fluid take to get foetal cells
risk of infection, miscarriage (1%) or Rh sensitisation
What DNA tests are done?
genetic disorder test, karyotype if family chromosomal abnormality, QF-PCR for T13, 18, 21
What are the reproductive options?
naturally conceive egg/sperm donor adopt no kids pre-implantation genetic diagnosis
How is egg/sperm donor carried out?
HEFA licensed fertility centre or private doctor
child has right to find donor at 18
Name and explain adoption stages
register/checks - criminal/medical background, 2 months
assessment/approval - social work home visit, prospective adopters report made and sent to panel for review, decision, 4 months
Explain PGD stages
stimulate ovaries and collect egg
inseminate and fertilise eggs
biopsy embryo and test
transfer the embryo and do pregnancy test
