prenatal genetics (10) Flashcards
what are some indications for prenatal screening?
Ultrasound anomaly, repeated miscarriages, abnormal MSAFP (maternal serum alphafetoprotein- high and low levels have been associated with fetal abnormalities), anxiety, environmental exposures (smoking, alcohol), increased risk of chromosomal abnormality
what is an example of a non invasive test for fetuses?
ultrasound
what are 3 invasive tests available for fetal testing?
cytogenetics, biochemical, molecular studies
when is an ultrasound first usually preformed
around 18 weeks
what is “nuchal translucency” and what is it associated with
may be associated with chromosome anomalies.
Very thick skin can be an indicator for downs syndrome
explain a closed vs open neural tube defect
open-no skin covering and neural tube fluid can leak in the amniotic sac
close-skin still covering the mutation
what is Maternal serum alphafetoprotein (MSAFP)? how can it be tested for? what age is it tested for at?
albumin like protein produced by fetal liver
can be tested for in the maternal blood
tested for around 15-20 weeks
what are some factors that must be known to make an accurate evaluation of a MSAFP value?
gestational age, mother’s weight (because the plot is based upon the mg of blood of the mother, a larger woman has more blood), race and diabetic status
what are low levels of MSAFP associated with?
down syndrome and other chromosome anomalies
what are high levels of MSAFP associated with?
neural tube defects
at what age is integrated prenatal testing done at?
10-13 weeks gestation
when and how is non-invasive prenatal screening done?
10-22 weeks gestation
cffDNA isolated from maternal blood
true or false
NIPS is extremely accurate for screening & diagnosing down syndrome
FALSE
yes nips is very accurate for DS (99%) but it is not a diagnostic study, it only gives risk for the chromosomal abnormality and needs to be confirmed with FISH or karyotyping
what age is amniocentesis done?
14-20 weeks gestation
usually done around 16-18 weeks
can be done as late as 35 weeks tho
what is the risk associated with amniocentesis?
1/200
what tests are possible with an aminocentesis
AFAFP, cytogenetics (karyotype & FISH), metabolic assays, molecular diagnostics
what test is used as a confirmatory test used in conjunction with high AFP levels?
acetylcholinesterase (AChE)
which is only present in the amniotic fluid if there is an open neural tube
what age is chorionic villus sampling done?
10-12 weeks gestation
what can be a consequence of doing a CVS before 10 weeks gestation?
limb reduction
what is the risk associated with CVS?
1/100
what tests can be done with CVS?
cytogenetics, molecular genetics, metabolic (cells only)
so if CVS is so risky why even do it?
Because you can do it 10-14 weeks and its a lot easier to terminate at this stage that any other
what is the procedure with in vitro fertilization
Egg retrieval from a female which is then mixed in vitro with partners sperm. Following fertilization, appropriate embryos are implanted in the woman’s uterus
what is the procedure with intracytoplasmic sperm insertion?
Single sperm is injected into an egg. Following fertilization embryos can be implanted into female. This is helpful for males with low sperm count
in a polar body analysis, what does it mean if the 1st polar body tests positive for a recessive mutation (like CF)? from a mother than is a CF carrier
then you would expect the oocyte NOT to have the mutation and be safe
tell me about the pre-implantation genetic diagnosis testing
eggs collected from mom & fertilized in vitro with dads sperm. At the 8 cell stage, a single cell is separated out and tested either by FISH or molecular assay
