Lecture 9: Prenatal Genetics Flashcards
(40 cards)
Is the recurrence risk for open neural tube defect high or low? why?
high
multifactorial; gene + env
What is MSAFP dnd what is an abnormality an indication for?
maternal serum alphafetoprotein
high/low –> fetal abnormalities
prenatal diagnosis
What are the most common aneuploidy and autosomal aneupolidy in spontaneous abortion?
45,X (95% will terminate spontaneously)
Trisomy 16
What are the non-invasive tests for prenatal genetics?
examination
ultrasound
Testing Maternal AFP
What are the invasive tests for prenatal genetics?
cytogenics biochemical molecular studies Testing fetal AFP Amniocentesis CVS
Why are some prenatal tests considered invasive?
needle inserted to collect fetal cells, tissues, or fluids
What does nuchal translucency on an ultrasound indicate?
possible xs abormality
What fetal anomalies can ultrasounds detect?
nuchal translucency, clefting, neural tube defects (NTD)
Where is AFP produced, and what is the test sensitive to?
produced in fetal liver, found in mother’s serum
test is sensitive to mother’s WEIGHT, race, diabetic status
What do high/low level of AFP indicate?
Low = down syndrome; xs anomaly High = NTD
is AFP used for diagnosis?
No - risk assessment
What method is used to detect Down Syndrome?
Maternal Serum Quad Test
If a lab cannot determine nuchal translucency as a screen for Down Syndrome, what tests can they offer?
PAPP-A + Maternal Serum Quad Test
what is NIPS(/NIPT)?
Non-Invasive Prenatal Screening(/Testing)
How and when is NIPS performed?
use cfpDNA (cell free placental) at 10-22 weeks
then sequence
use precise software to analyze aneuploidies present
After NIPS, how would diagnosis be performed?
Karyotype analysis
FISH on amniotic fluid
Which is more accurate: NIPS or serum screening?
NIPS
What is amniocentesis? When is it performed?
Needle goes into amniotic cavity, draws amniotic fluid
16-18 weeks
early: 13/14 weeks
Which is more risky - early or later amniocentesis? Why?
early is riskier
not as much amniotic fluid - could remove too much –> loss of mobility of fetus –> developmental defects
What tests can be performed after amniocentesis?
AFAFP (like MFAFP)
Cytogenetics
Metabolic Assays
Molecular diagnostics
what must be know for AFAFP/MFAFP testing?
gestational age
known standards for comparison
What are low AFP levels indicative of?
Trisomies 13, 18, 21
Mosaic Turner Syndrome
Tiploidy
Unbalanced translocations
What are high levels of AFP indicative of?
teratoma renal obstruction/agenesis uropathy upper GI obstruction bladder/cloacal exstrophy
What are reasonable explanations for increased AFP levels??
gestational age incorrectly reported
mom’s weigh nigh/low
twins
