prenatal genetics (10)

Question 1

what are some indications for prenatal screening?

Answer 1

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

Question 2

what is an example of a non invasive test for fetuses?

Answer 2

ultrasound

Question 3

what are 3 invasive tests available for fetal testing?

Answer 3

cytogenetics, biochemical, molecular studies

Question 4

when is an ultrasound first usually preformed

Answer 4

around 18 weeks

Question 5

what is “nuchal translucency” and what is it associated with

Answer 5

may be associated with chromosome anomalies.

Very thick skin can be an indicator for downs syndrome

Question 6

explain a closed vs open neural tube defect

Answer 6

open-no skin covering and neural tube fluid can leak in the amniotic sac
close-skin still covering the mutation

Question 7

what is Maternal serum alphafetoprotein (MSAFP)? how can it be tested for? what age is it tested for at?

Answer 7

albumin like protein produced by fetal liver
can be tested for in the maternal blood
tested for around 15-20 weeks

Question 8

what are some factors that must be known to make an accurate evaluation of a MSAFP value?

Answer 8

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

Question 9

what are low levels of MSAFP associated with?

Answer 9

down syndrome and other chromosome anomalies

Question 10

what are high levels of MSAFP associated with?

Answer 10

neural tube defects

Question 11

at what age is integrated prenatal testing done at?

Answer 11

10-13 weeks gestation

Question 12

when and how is non-invasive prenatal screening done?

Answer 12

10-22 weeks gestation

cffDNA isolated from maternal blood

Question 13

true or false

NIPS is extremely accurate for screening & diagnosing down syndrome

Answer 13

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

Question 14

what age is amniocentesis done?

Answer 14

14-20 weeks gestation
usually done around 16-18 weeks
can be done as late as 35 weeks tho

Question 15

what is the risk associated with amniocentesis?

Answer 15

1/200

Question 16

what tests are possible with an aminocentesis

Answer 16

AFAFP, cytogenetics (karyotype & FISH), metabolic assays, molecular diagnostics

Question 17

what test is used as a confirmatory test used in conjunction with high AFP levels?

Answer 17

acetylcholinesterase (AChE)

which is only present in the amniotic fluid if there is an open neural tube

Question 18

what age is chorionic villus sampling done?

Answer 18

10-12 weeks gestation

Question 19

what can be a consequence of doing a CVS before 10 weeks gestation?

Answer 19

limb reduction

Question 20

what is the risk associated with CVS?

Answer 20

1/100

Question 21

what tests can be done with CVS?

Answer 21

cytogenetics, molecular genetics, metabolic (cells only)

Question 22

so if CVS is so risky why even do it?

Answer 22

Because you can do it 10-14 weeks and its a lot easier to terminate at this stage that any other

Question 23

what is the procedure with in vitro fertilization

Answer 23

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

Question 24

what is the procedure with intracytoplasmic sperm insertion?

Answer 24

Single sperm is injected into an egg. Following fertilization embryos can be implanted into female. This is helpful for males with low sperm count

Question 25

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

Answer 25

then you would expect the oocyte NOT to have the mutation and be safe

Question 26

tell me about the pre-implantation genetic diagnosis testing

Answer 26

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