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RDS Test 4 > B8.066 Preconceptual and Prenatal Genetic Screening and Counseling > Flashcards

B8.066 Preconceptual and Prenatal Genetic Screening and Counseling Flashcards

1
Q

prenatal

A

pertaining to the state of pregnancy at any gestational age prior to delivery

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2
Q

preconception

A

any person (men and women) with reproductive potential

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3
Q

chromosomal disorders

A

affect number or structure of chromosomes

  • Down Syndrome
  • del22q11.2 (digeorge)
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4
Q

genetic disorders

A

affect the structure and function of genes

  • cystic fibrosis
  • tay sachs
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5
Q

preconception care

A

identifiation of conditions that could affect a future pregnancy or fetus and that may be amenable to intervention

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6
Q

what is included in preconception care?

A 
family planning and pregnancy spacing
current meds
nutrition
immunization status
review of med, surg, psych history
socioeconomic, educational, and cultural context
exercise history
family history*
genetic screening/testing*
substance abuse
OB/GYN history
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7
Q

recommended genetic carrier screening

A

CF
spinal muscular atrophy
hemoglobinopathies
fragile x
genetic conditions based on eastern /central european jewish descent
genetic conditions based on founder mutations

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8
Q

recommendation for CF carrier screening

A

offer to all women who are considering pregnancy or are currently pregnant

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9
Q

which groups have the highest carrier rates of CF?

A

Ashkenazi Jewish

Non-hispanic white

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10
Q

CFTR protein

A

25 exons
250,000 bp
1480 aa
transmembrane Cl- channel > complex product

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11
Q

considerations for CF screening

A
  • populations with lower carrier frequencies also have higher rates of atypical mutations (aka easier to catch mutations in populations with more prevalence)
  • 80% of men with congenital bilateral absence of the vas deference have CFTR mutations
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12
Q

what do you do if an individual screens positive as a carrier for CF

A

DO NOT use a common mutation panel for their partner….need to do full sequencing

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13
Q

what populations are most at risk of SMA

A

caucasian
ashkenazi jewish
asian

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14
Q

what is the normal gene structure of SMA?

A

SMN1 + SMN 2 on each chromosome

SMN2 produces a functional product, but at a very low amount, doesn’t contribute much to disease process

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15
Q

most common SMA genetic mutation

A

93%
missing SMN1 on both chromosomes
due to crossing over event that excises SMN1 in each parent

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16
Q

less common SMA genetic mutation

A

6%
1 chromosome with SMN1 missing
1 chromosome with mutations that makes SMN1 nonfunctional

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17
Q

very rare SMA genetics mutation

A

1 in 1000
happens in consanguineous relationships
SMN1 on both chromosomes have mutations that make them nonfunctional

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18
Q

ways that you can be a carrier for SMA

A

carrier of deletion
carrier of mutation
2+0 carrier

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19
Q

what is a 2+0 carrier of SMA and why is this an issue

A

these people have 2 SMN1 copies on 1 chromosome and a deleted SMN1 on the other chromosome; but still technically have 2 copies
carrier screening typically only looks for # of SMN1 copies, so this person can appear to be normal on screening

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20
Q

how could you recognize a 2+0 carrier

A

look for a g.27134 T>G mutation in one of the copies

more common in african american populations

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21
Q

carrier screening recommendation for hemoglobinopathies

A

a CBC with RBC indices should be performed on all women who are currently pregnant to assess not only their risk of anemia, but also allow assessment for risk of a hemoglobinopathy
*ideally offered before pregnancy

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22
Q

B globin gene cluster

A

chromosome 11
gamma product > contributes to Hb F
delta product > contributes to HbA2
beta product > contributes to HbA

23
Q

alpha globin gene cluster

A

chromosome 16
zeta 1&2
alpha 1&2

24
Q

most common hemoglobinopathies

A

sickle cell/ hemoglobin variants of the B chain
B Thalassemia
a Thalassemia

25
Q

how do you screen for hemoglobinopathies

A

hemoglobin electrophoresis should be performed in addition to a CBC if there is suspicion of a hemoglobinopathy based on ethnicity (african, mediterranean, middle eastern, southeast asian, west indian)

26
Q

what would indicated B-Thalassemia trait on CBC and Hb electrophoresis

A

MCV < 80
increased HbA2 (>3.5%)
-indicates that not enough B chain is being made

27
Q

what would indicated a-Thalassemia trait on CBC and Hb electrophoresis

A

MCV <80

no iron deficiency

28
Q

what do you do if you find an a or B thalassemia trait?

A

test partner!

29
Q

what other lab finding would lead to testing a partner for hemoglobinopathies

A

clinically significant Hb variant on electrophoresis

-cant detect absence, only abnormal product

30
Q

who should be screened for fragile x premutation

A

women with a family history of fragile x related disorders or intellectual disability suggestive of fragile x syndrome
women with unexplained ovarian insufficiency or failure before age 40

31
Q

CGG repeat levels in fragile x

A

normal : 5-44
intermediate: 45-54 (at risk for expansion only to premutation)
premutation: 55-200 (increased risk for FXTAS and POF)
full mutation: 201 and up (fragile x syndrome)

32
Q

role of AGG interruption within maternal FMR1 gene

A

reduces the risk of offspring with fragile x

33
Q

most common disorders in ashkenazi jewish populations

A 
gaucher disease
CF
tay sachs
familial dysautonomia
canavan disease
34
Q

less common, but severe disorders in the ashkenazi jewish populations

A

fanconi anemia
niemann-pick type A
bloom syndrome
mucolipidosis IV

35
Q

what are some qualifications for disorders to be selected for expanded carrier panels

A

carrier frequency of 1 in 100 or greater
have a well defined phenotype
have a detrimental effect on quality of life
cause cognitive or physical impairment
require surgical or medical intervention
have early onset
screened conditions should be able to be diagnosed prenatally
should not include disorders of adult onset

36
Q

purpose and target population of screening tests

A

purpose: to detect potential disease indicators
target population: large numbers of asymptomatic, but potentially at risk individuals
**sensitive

37
Q

purpose and target population of diagnostic tests

A

purpose: to establish presence/absence of a disease
target population: symptomatic individuals to establish diagnosis, or asymptomatic individuals with a positive screening test
**specific

38
Q

screening for chromosome abnormalities in the first trimester

A 
nuchal translucency
nasal bone
ductus venosus
tricuspid defects
maternal serum screening
39
Q

nuchal translucency testing

A

performed by US between 11w and 13w6d

normal is under 2.5-3 mm depending on gestational age

40
Q

increased NT

A

associated with cardiac defects and chromosome abnormalities

41
Q

nasal bone testing

A

screening for presence or absence only

low nasal bridge associated with some chromosome abnormalities

42
Q

maternal serum screening in 1st trimester

A

PAPP-A
BhCG
AFP (placental, not fetal, different from AFP done in 2nd trimester to test for neural tube defects)

43
Q

purpose of maternal serum testing in 1st trimester

A

adjusts risk for trisomies 18 and 21

44
Q

components of maternal serum screening in 2nd trimester for chromosomal abnormalities

A

hCG
AFP
DIA
uE3

45
Q

how are maternal serum levels analyzed

A

multiples of means

normal distributions of affected and unaffected individuals

46
Q

AFP levels in down syndrome

A

low

47
Q

AFP levels in spina bifida

A

high

48
Q

function of maternal serum screening in 2nd trimester for chromosomal abnormalities

A

performed between 15w and 22w6d
correct assessment of gestational age is critical for interpretation
detection for trisomy 21, 18 and neural tube defects

49
Q

screening options for chromosome abnormalities that can be done in all trimesters

A

non-invasive prenatal screening
may be performed anytime after 10 weeks of gestation
cfDNA analyzed in fetus and mother

50
Q

functions of screening methods for chromosome abnormalities that can be done in all trimesters

A

screens for trisomy 13, 18, 21 and abnormal numbers of sex chromosomes
may be used to detect microdeletions (del22q11.2, cri-du-chat (5p), angelman/ prader willi, wilf hirshorn (4p), and 1p36 deletion syndrome)
can screen for all chromosomes!!!

51
Q

diagnostic testing for chromosome abnormalities and genetic disorders

A

amniocentesis

chorionic villus sampling

52
Q

amniocentesis

A

after 15 weeks

53
Q

chorionic villus sampling

A

between 10-14 weeks

54
Q

what can fetal cells be used for after amniocentesis/ chorionic villus sampling

A 
chromosome analysis
microarray analysis
single gene analysis
analyte analysis (only amnio)
WES, WGS

RDS Test 4 (17 decks)

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