Pre-Natal Testing Flashcards
What are the components of prenatal testing?
- prenatal screening
- prenatal diagnosis
Contrast prenatal screening and prenatal diagnosis
- prenatal screening: focuses on finding problems among large population with affordable and non-invasive methods (eg. downs syndrome, blood borne viruses etc)
- prenatal diagnosis: focuses on pursuing additional detailed information once a problem has been found and can sometimes be more invasive (eg. chorionic villus sampling)
What is the purpose of prenatal testing?
- enable timely medical/surgical treatment of a condition before or after birth
- give parents chance to terminate pregnancy with diagnosed condition
- give parents the chance to prepare physiologically, socially, financially, and medically for baby with health problem/disability/likelihoof stillborn
- organise fetal surveillance
What are the types of screening during pregnancy?
- blood tests (FBC, blood group and rhesus state, haemoglobinopathies, infectious disease, chromosomal disorders)
- USS
- questionnaire
Describe the first trimester combined test
Uses:
- maternal age
- nuchal translucency measurement
- free beta hCG and PAPP-A
- gestational age
- done from 11-14 weeks
- results show whether high or low chance of having a baby with Down’s Syndrome
Describe the second trimester screening
Uses:
- maternal age
- biomarkers
- done 14-20 weeks
- not as good at detecting Down’s/Edward’s/Patau’s Syndrome
What are the further options for women who have higher-chance result 1:150 from first or second trimester screening?
- no further tests
- more accurate blood screening NIPT
- diagnostic tests: chorionic villus sampling or amniocentesis
Describe NIPT
- screening so not diagnostic
- from 10 weeks
- cell free DNA extracted and analysed from maternal blood test
- results given as low or high chance result
- if low chance then no further tests offered
Describe chorionic villus sampling
- fine needle inserted through abdomen and into uterus or through cervix, and small piece of developing placenta removed
- done from 11 weeks
- tests for inherited disorders (eg. CF, sickle cell, thalassaemias, DMD)
Describe amniocentesis
- needle inserted through abdomen and into amniotic fluid which is aspirated
- used for karyotyping if screening suggests aneuploidy
- from 15 weeks
Describe ultrasound screening
- dating scan at 12 weeks for:
- number of pregnancies
- viability
- gestational weeks
- NT thickness
- NT defects
- anomaly scan at 20 weeks for:
- physical abnormalities (eg. spinda bifida, placental position)
Describe preimplantation genetic diagnosis (PGD)
- offered to couples who risk passing on genetic disorder
- removal of 1 cell from early embryo
- uncommon and expensive
What disorders is PGD acceptable for?
- a disorder that may affect capacity for live birth
- risk of child being born with or developing a serious disability
- eg. CF, fragile X syndrome, blood disorders etc.
What are things to consider in the seriousness of a disability/disorder?
- views of those seeking treatment
- likely degree of suffering
- availability of effective treatment
- speed of degeneration
- extend of intellectual impairment
- family circumstances
What is CRISPR gene editing?
- genetic engineering technique which involves genomes of living organisms are modified
- allows genomes to be edited in vivo with high precision, cheaply and with ease and can be used to make new medicines