Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Practice bulletins > #163 Screening for Fetal Aneuploidy > Flashcards

#163 Screening for Fetal Aneuploidy Flashcards

1
Q

What is the definition of aneuploidy?

A

Having or or more extra or missing chromosomes, leading to an unbalanced chromosome number in a cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How often do chromosomal abnormalities occur in live births?

A

1 in 150 live births

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Is rate of fetal aneuploidy increased with certain race or ethnic groups?

A

No, not related to race or ethnicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What factors increase risk of fetal aneuploidy?

A

Increasing age, history of prior aneuploid fetus, presence of fetal anomalies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the most common aneuploidies that are not related to sex chromosome disorders?

A

Trisomies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the prevalence of Down syndrome?

A

Approximately 1 in 800 live births

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the most common sex chromosome aneuploidy? What is its prevalence?

A

Klinefelter syndrome (47, XXY) with prevalence of 1 in 500 males

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the only viable monosomy?

A

Turner syndrome (45, X)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the most common cause of Down syndrome?

A

95% of cases resulted from nondisjunction involving chromosome 21 (remaining cases translocations or somatic mosaicism)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the clinical presentation of Down syndrome?

A

Associated with characteristic facial features, learning disabilities, congenital heart defects, intestinal atresia, seizures, childhood leukemia, early-onset Alzheimer disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What percentage of pregnancies affected by Down syndrome do not survive between first trimester and full term?

A

Estimated 43% end in miscarriage or stillbirth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

In economically developed countries, what is the median survival of individuals with Down syndrome?

A

Almost 60yo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Can prenatal assessment predict the severity of complications from Down syndrome?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What should you do for a woman with a positive aneuploidy screening test?

A

Offer option of diagnostic testing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What screening tests for aneuploidy are available?

A

First-trimester, triple, quad, and penta screens; cell-free DNA; and ultrasonographic screening (single screening tests). Integrated, sequential, and contingent screening (performed in first and second trimesters)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

At what crown-rump length measurement range can you perform first-trimester screening?

A

Between 38-45mm and 84mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

At what gestational age range can you typically perform first-trimester screen?

A

10w0d to 13w6d. It really depends on CRL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What components are part of first-trimester screen?

A

Nuchal translucency measurement, serum free beta-hcg (or total hcg), pregnancy-associated plasma protein A (PAPP-A)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the definition of enlarged nuchal translucency?

A

3.0mm or more or above 99th percentile for CRL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

True or false: enlarged nuchal translucency is independently associated with fetal aneuploidy and structural malformatinos?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

During what gestational age range can you perform a quadruple (“quad”) screen? When is best time to run it and why?

A

15w0d to 22w6d. dependent on laboratory. Best time is from 16-18wks, optimizes screening for neural tube defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What serum analytes are included in quad screen?

A

hcg, AFP, inhibin A, estriol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the detection rate for Down syndrome in first trimester screen? What percent of pregnancies screen positive?

A

82-87%. 5% screen positive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the detection rate for Down syndrome in triple screen? What percent of pregnancies screen positive?

A

69%. 5% screen positive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the detection rate for Down syndrome in quad screen? What percent of pregnancies screen positive?

A

81%. 5% screen positive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the detection rate for Down syndrome in integrated screen? What percent of pregnancies screen positive?

A

96%. 5% screen positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the detection rate for Down syndrome in sequential stepwise screen? What percent of pregnancies screen positive?

A

95%, 5% screen positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the detection rate for Down syndrome in contingent screeningWhat percent of pregnancies screen positive?

A

88-94%, 5% screen positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the detection rate for Down syndrome in serum integrated screen? What percent of pregnancies screen positive?

A

88%, 5% screen positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the detection rate for Down syndrome in cell-free DNA screen? What percent of pregnancies screen positive?

A

99% (in patients who receive a result), 0.5% screen positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

At what gestational age can you run a cell-free DNA screen?

A

From 10wks to term

32
Q

What is the detection rate for Down syndrome w/ nuchal translucency screen? What percent of pregnancies screen positive?

A

64-70%, 5% screen positive

33
Q

What is the penta screen?

A

Aneuploidy screening during second trimester w/ hcg, estriol, AFP, inhibin A, and hyperglycosylated hcg (AKA invasive trophoblast antigen). Limited data available to compare accuracy with other second-trimester screens

34
Q

What analytes are in the triple screen?

A

hcg, AFP, unconjucated estriol. Lower sensitivity than quad and first-trimester screening

35
Q

What are the protocols for combined first- and second-trimester screening?

A

Integrated, sequential, or contingent

36
Q

What is integrated aneuploidy screening?

A

Patient undergoes a first-trimester nuchal translucency and analyte screening followed by second-trimester quad screen and receives single result in second trimester

37
Q

What is stepwise sequential aneuploidy screening?

A

Patient is given a preliminary risk estimate after completion of first-trimester screen. If screen positive, patient offered diagnostic test or cell-free DNA screening and screening protocol discontinued. If negative screening, proceed to quad screen in second trimester

38
Q

What is contingent sequential screening?

A

Aneuploidy risk after first-trimester screen classified as high, intermediate, or low. High risk are offered cell-free DNA screen or diagnostic testing. Low risk given no further screening. Intermediate risk offered quad screen.

39
Q

Is it recommended for patients to undergo multiple aneuploidy screening tests performed independently (unlinked)?

A

No, will result in unacceptably high positive screening rate

40
Q

What is the name of syndrome with trisomy 13?

A

Patau syndrome

41
Q

What is rate of Patau syndrome (trisomy 13)?

A

1 in 10,000 births

42
Q

What is the name of syndrome with trisomy 18?

A

Edwards syndrome

43
Q

What is rate of Edwards syndrome (trisomy 18)?

A

1 in 6,000

44
Q

What chromosome abnormality is associated with Patau syndrome?

A

Trisomy 13

45
Q

What chromosome abnormality is associated with Edwards syndrome?

A

Trisomy 18

46
Q

What are the major structural anomalies associated with fetal Down syndrome?

A

Cardiac anomalies (septal defects, tetralogy of Fallot, AV canal defects), duodenal atresia

47
Q

What are soft ultrasonographic markers for aneuploidy?

A

Thickened nuchal fold, renal pelvis dilation, echogenic bowel, intracardiac echogenic focus, choroid plexus cyst, shortened humerus or femur length, hypoplastic or absent nasal bone, cystic hygroma, ventriculomegaly

48
Q

What soft ultrasonographic marker for aneuploidy has the highest risk of aneuploidy as an isolated finding?

A

Increased nuchal skinfold thickness

49
Q

What isolated soft ultrasonographic marker has the lowest risk of fetal aneuploidy?

A

Isolated echogenic intracardiac focus

50
Q

For prenatal ultrasound, which isolated ultrasonographic soft markers require follow up?

A

renal pelvis dilation, echogenic bowel, shortened humerus or femur length

51
Q

Where does fetal cell-free DNA come from?

A

Fetal component is released into maternal circulation primarily from placental cells undergoing apoptosis

52
Q

What is the normal fetal fraction of cell-free DNA?

A

3-13%, increases throughout gestation

53
Q

How soon after delivery do you expect fetal cell-free DNA to be cleared from maternal circuluation?

A

Within hours after childbirth

54
Q

True or false, women with “no reportable result” with cell free DNA screening are at increased risk of fetal aneuploidy?

A

True

55
Q

Does increased nuchal translucency increase risk of anything beyond aneuploidy?

A

Yes. Increased risk of genetic syndromes and isolated anomalies, such as congenital heart defects, abdominal wall defects, and diaphragmatic hernia

56
Q

What should you offer patient’s with increased nuchal translucency?

A

Genetic counseling. Diagnostic genetic testing. Targeted ultrasound exam and fetal echo in second trimester

57
Q

What does a cystic hygroma look like in first trimester?

A

Increased nuchal translucency extending along the length of the fetus in which septations are clearly visible

58
Q

What percentage of pregnancies with cystic hygroma will result in healthy live-born infants at term?

A

Less than 20%

59
Q

What additional screening should be offered to women who undergo first trimester screen?

A

Second-trimester assessment for open fetal defects by ultrasound, MSAFP screening, or both

60
Q

What can a positive screening test result from cell-free DNA screening represent apart from fetal aneuploidy?

A

Confined placental mosaicism, a resorbing twin, maternal malignancy or maternal aneuploidy

61
Q

What is the positive predictive value of cell-free DNA testing for down syndrome, trisomy 18, trisomy 13, and sex chromosome aneuploidy?

A

Down - 93%
Trisomy 18 - 64%
Trisomy 13 - 44%
Sex chromosome - 39%

62
Q

What factors contribute to low fetal fraction on cell-free DNA screen?

A

Sampling before 10 wks, high maternal BMI, fetal aneuploidy

63
Q

What percent of cell-free DNA screens that fail to obtain a result are aneuploid?

A

22%, according to one study of more than 1,000 analyzed samples

64
Q

How should you manage a low fetal fraction result on cell-free DNA screening?

A

Repeat cell-free DNA screening or do diagnostic testing

65
Q

What is the recommendation after positive cell-free DNA screening result?

A

Diagnostic testing. Not recommended to pursue pregnancy termination based off cffDNA results

66
Q

Does cffDNA screening offer information regarding potential for open fetal defects?

A

No. Patients should undergo ultrasound, MSAFP screening, or both

67
Q

What is the residual risk of a chromosomal abnormality with a normal cffDNA screening after an abnormal traditional screening test?

A

2%

68
Q

What obstetrical complications are associated with a PAPP-A level below 5th %tile in first trimester?

A

Spontaneous fetal and neonatal loss, fetal growth restriction, preeclampsia, placental abruption, preterm delivery

69
Q

In second trimester, elevated hcg, AFP, and inhibin A levels in pregnancies without structural anomalies are associated with what?

A

Increased risk of fetal death, IUGR, and preeclampsia

70
Q

If a patient conceives and has undergone preimplantation genetic screening, should prenatal aneuploid screening be offered?

A

Yes, because false-negative results can occur with preimplantation genetic screening

71
Q

Is the risk of having aneuploid fetus higher in monozygotic twins or dizygotic twins?

A

Dizygotic. Each fetus carries risk of aneuploidy similar to mother’s age-adjusted risk, but mother carries increased risk of having a fetus with aneuploidy because there is more than one fetus. Monozygous typically is all or none.

72
Q

Are aneuploidy screening tests as accurate in twin gestations as singletons?

A

No, but can still be used for twin gestations (do not use for higher-order multifetal gestations). Nuchal translucency allows for each fetus to be independently screened.

73
Q

What can a single enlarged nuchal translucency in monochorionic twins of discordant size indicate?

A

Early sign of twin-twin transfusion , rather than aneuploidy

74
Q

In multifetal gestation, if fetal demise or anomaly is identified in one fetus, can you use serum-based aneuploidy screening?

A

Should be discouraged, significant risk of an inaccurate test result

75
Q

Are cell-free DNA screening tests useful for assessing for microdeletions?

A

Has not been validated clinically and not recommended at this time

Practice bulletins (83 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions