Prenatal Cytogenetics

Question 1

Incidence of aneuploidy in sperm, oocytes and preimplantation embryos?

Answer 1

1-2% sperm, 20% oocytes and 20% preimplantation embryos

Question 2

4 common aneuploidies (35%) of spontaneous abortions?

Answer 2

45, X, +16, +21, +22

Question 3

3 common aneuploidies (4%) of stillbirths?

Answer 3

+13, +18 and +21

Question 4

6 common aneuploidies of live births?

Answer 4

+13, +18 and +21
XXX, XXY (Klinefelters), XYY (Jacobs)

Question 5

Risk of recurrent aneuploidy?

Answer 5

1-1.5% until AMA

Question 6

True of false? 45, X associated with AMA

Answer 6

False, paternal risk

Question 7

Young maternal age range risk for aneuploidies

Answer 7

13 to 20

Question 8

3 risks with advanced paternal age (APA)?

Answer 8

1. Structural abnormalities
2. Point mutations (achondroplasia)
3. Schizophrenia or mental illness

Question 9

Risk for aneuploidy at 20, 35 and 41?

Answer 9

1 in 1152, 1 in 240 and 1 in 41 (first trimester Down syndrome)

Question 10

Protein complex degraded in AMA and prolonged prophase arrest?

Answer 10

cohesin

Question 11

Nuchal translucency increased at ______ mm and measured at _______ to ______ weeks

Answer 11

2.5 mm (or 3), 11-14 weeks

Question 12

Absent nasal bone marker more common in which population?

Answer 12

Afro-Carribean

Question 13

Echogenic cardiac focus marker more common in which population?

Answer 13

Asians

Question 14

Likelihood ratio for echogenic intracardiac focus marker?

Answer 14

1.7

Question 15

Likelihood ratio for echogenic bowel and cystic fibrosis/placental bleed?

Answer 15

6.7

Question 16

Up to 48% of fetuses with ________ anomaly will have a chromosome anomaly

Answer 16

cardiac (think aneuploidy, Noonan, 22p11.2)

Question 17

Triploidy incidence and % of pregnancy loss

Answer 17

1 in 1000, 8-10% of pregnancy loss

Question 18

Complete mole karyotype and entirely _________ (maternally, paternally) derived

Answer 18

46, XX (90%) or 46, XY (10%) (90% two sperm, 10% diploid sperm) and paternally
- no embryo
- hydropic villi

Question 19

Complete mole risk for trophoblastic disease and choriocarcinoma

Answer 19

trophoblastic disease - 15-20%
choriocarcinoma - 2-4%

Question 20

Incomplete mole karyotype and risk of gestational trophoblastic disease and preeclampsia

Answer 20

69
4% risk of trophoblastic disease
35% risk of preeclampsia

Question 21

Incomplete moles are most commonly caused by diploid ______ fertilized by _______ sperm

Answer 21

Diploid egg, haploid sperm (30-40% of cases)
69,XXX (37%) or 69,XXY (60%) or 69,XYY (3%)

Question 22

Year for first amniocentesis with karyotype?

Answer 22

1956

Question 23

Year for chorionic villous sampling?

Answer 23

1983

Question 24

Year for first chromosomal microarray (CMA)?

Answer 24

2010

Question 25

Year for cell free NIPT?

Answer 25

2011

Question 26

Year for prenatal WES or WGS?

Answer 26

WES - 2013
WGS - 2017 (not commercially available)

Question 27

_____ ________ ________ is when the placenta has chromosome anomaly while fetus is unaffected (0.8-2% at 8-11 weeks)

Answer 27

confined placental mosaicism (CPM)

Question 28

Maternal and NIPT are ______________ tests

Answer 28

screening tests

Question 29

amniocentesis, CVS and cord blood are ___________ tests

Answer 29

diagnostics

Question 30

On maternal serum screening trisomy 21 is associated with increased?

Answer 30

hCG and inhibin A

Question 31

On maternal serum screening neural tube defects are associated with increased?

Answer 31

AFP

Question 32

cfDNA in NIPT is ~ ______ bp in length

Answer 32

200

Question 33

NIPT performed after _______ weeks

Answer 33

10

Question 34

NIPT may use either ____________ sequencing or ___________ sequencing

Answer 34

random, targeted (SNP cannot tell homozygosity from deletion)

Question 35

NIPT abnormalities detected?

Answer 35

1. Trisomies (+13, +18, +21)
2. Sex chromosome anomalies 45, X/47, XXX/ 47, XXY/ 47, XYY
3. Triploidy

Question 36

PPV in NIPT is only about 90% for which 3 disorders?

Answer 36

+21, +18, sex chromosome abnormalities
*also depends on age (as prevalence changes)

Question 37

3 reasons for false positive NIPTs?

Answer 37

1. CPM - confined placental mosaicism
2. Reabsorbed twin
3. Maternal conditions

Question 38

2 reasons for false negative NIPTs?

Answer 38

1. Fetal mosaicism
2. Partial trisomy

Question 39

4 Maternal causes of NIPT no call

Answer 39

1. obesity (too many maternal cells)
2. anticoagulation
3. B12 deficiency
4. maternal cancer
5. maternal bone marrow transplant

Question 40

3 Fetal causes of NIPT no call

Answer 40

1. Twin demise
2. Triplets
3. GA too early

Question 41

Sensitivity for trisomy 21 first and second trimester serum screening as well as combined?

Answer 41

85% first trimester
81% second trimester
95% combined

Question 42

False positive rate for trisomy 21 by serum screening and NIPT?

Answer 42

serum - 5%
NIPT - 1%

Question 43

Amniocentesis is performed after __________ weeks

Answer 43

15.5

Question 44

Amniocentesis miscarriage risk:

Answer 44

1/200 to 1/1000

Question 45

Amniocentesis risk after 24 weeks

Answer 45

Preterm delivery

Question 46

3 uses of amniocentesis

Answer 46

1. Genetics
2. Fetal lung assessment
3. Remove excess fluid

Question 47

Chorionic villous sampling performed between _______ and _______ weeks

Answer 47

11-14 weeks

Question 48

CVS risk

Answer 48

1 in 100 to 1/1000

Question 49

Umbilical cord/cordocentesis performed at _______ to _______

Answer 49

17-20 weeks

Question 50

Miscarriage risk ____ to _____ % for cordocentesis/umbilical cord sampling

Answer 50

1-7%

Question 51

5% of couples with _____+ miscarriages/anomalous pregnancies have a chromosome rearrangement

Answer 51

3 miscarriages

Question 52

Maternal cell contamination/gestational cell contamination source in CVS?

Answer 52

Decidua contamination in CVS (1-2%)