prenatal testing Flashcards
role of prenatal screening and diagnosis
- Diagnosis of fetal abnormalities
- Assessment of the risk in pregnancy
- Prognosis
is the length of baby proportional to gestation
YEA
common prenatal problems
Structural abnormalities:
Heart
Brain
Spine
Genetic Disorders
Single gene (AD,AR, XD,XR)
Chromosomal (trisomy, deletion, duplication, translocation)
Mitochondrial (mitochondrial myopathy)
2 main categories of prenatal testing
non-invasive and invasive
3 examples of invasive testing
amniocentesis, chorionic villous sampling, foetal blood sample- from umbilical cord
3 examples of non-invasive testing
US
foetal brain MRI
4D scan
what can non-invasive tests tell us
Diagnosis of fetal structural abnormalities
what is the cell free fetal DNA test?
foetal DNA in maternal blood is collected
DNA isolation
PCR amplification
DNA sequencing
what is mosaicism
Mosaicism: can lead to false positives if placenta has the abnormality and the foetus does not. Always follow up a positive result with a diagnostic test.
what can invasive techniques tell us
Diagnosis of chromosomal, genetic problems, others (anemia)
Therapeutic tool (transfusion, laser, shunts etc)
ethical considerations for invasive prenatal testing
Risk of miscarriage (fetus may be normal)
Termination (decision has lifelong culpability, religious beliefs, rights of woman/baby)
Continuation of pregnancy (cost, impact on daily life, choice)
Will it make a difference? (treatable condition vs lethal abnorm)
when is chorionic villous sampling done?
10-13w
what is the risk of pregnancy loss from CVS
1%
how is CVS done?
Transabdominal, thin needle Ultrasound guided Usually no local required Outpatient Quick (5 min or less for actual procedure)
when is a CVS conducted?
increased combined risk >!:150 at term
consider: maternal age, US, biochemistry
