Prenatal diagnosis Flashcards
Current screening available?
Integ prenatal screening
1T screening
Quadruple maternal serum screeing
Nuchal translucency - greater than 3.5 mm is elevated - would send for detailed scan
Non-invasive chr eval
Fetal cells in maternal circ
PGD
Invasive chr eval
Amniocent
Chorionic villus tissue from placenta
Fetal blood
Amniocentesis
Take fluid - culture cells (chr anal/PCR) and test fluid (biochem)
Complications - pregnancy loss, leakage of amniotic fluid, amnionitis, vaginal bleeding, puncture fetus
CVS
Fibroblast-like cells of villus stroma - accurate rep of chr of fetus
What is mosaicism?
True - 2 abnormal cell lines detected in 2+ cultures from same individual
Pseudo - 2 abnorm cell lines found in 1 culture
Clinical outcomes of mosaicism?
depends on
- specific chr inv
- number of trisomic cells in placenta/fetus
Trisomy in CVS?
- only in placenta - doesn’t affect fetus/placenta
- placenta - affects placenta (IUGR)
- Trisomy in placenta/fetus
- trisomy in placenta and uniparental disomy in fetus
Triosomy in amniotic fluid?
More than likely in fetus but need US to assess
Uniparental disomy
2 copies of chr from one parent
trisomic rescue or monosomic rescue
gamete complementation
gamete complimentation
fert of gamete with 2 copies of same chr by gamete with no copies
Factors considered in PNT
Chr involvedn Tissue affect and level of trisomy method of ascertainment US findings Presence of UPD Previous case reports
NIPT
Blood test offered to:
older women, +ve mat serum screening, abnorm US, prior aneup
Aims of NIPT
Decreased risk
Decrease false pos
Increased detection rate
Easy testing
How is NIPT carreid out
cfDNA from fetus is in maternal blood
reliable detection after 7 weeks
seq cfDNA and compare against reference
