Module 6: Chromosomal Abnormalities Flashcards by Julianna Small

What is the most common abnormality among spontaneously aborted fetuses?

Turner’s (45xo)

95% are aborted

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What is non-disjunction?

The meiotic error that causes aneuploidy where a chromosome pair fails to separate during meiosis.

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What is the value of mild renal dilation?

Greater than or equal to 5mm

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What is the prognosis of T13?

Lethal/poor

70% are still born
85% die in 1st year

Survivors = profound mental retardation

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What is another name for T18?

Edward syndrome

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What heart defects are seen with T13?

- Hypoplastic left heart

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What are the levels on the triple screen in the presence of T18?

MS-AFP decreased

uE3 decreased

B hCG decreased

(All decreased)

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What heart defect is most common in T18?

Large VSD

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What is PAPP-A?

Pregnancy Associated Plasma Protein A

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Why are autosomal trisomies rarely seen?

Lethal (SA)

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How can clinodactyly be identified on U/S?

Overlapping digits in fist

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What is another name for T13?

Patau syndrome

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What is the triple screen detection rate of trisomy 21?

60%

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What is the prognosis of Turners babies that survive birth?

Few life threatening anomalies and normal intellect

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What increases the risk of T13?

Advanced maternal age

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How often do chromosomal abnormalities occur?

1/160 live births

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What increases the risk of trisomy 21?

Maternal age

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What is a marker for Triploidy?

Markedly high BhCG (8x higher than normal)

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What is Micrognathia?

Underdeveloped jaw

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What is the chromosome make-up in aneuploidy?

A sperm or oocyte has 2 copies of a particular chromosome or no copies instead of one copy in the haploid state.

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What is Cystic hygroma?

Multiple cysts in lymphatic system

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What is the 2nd most common chromosome abnormality at birth?

T18/Edwards

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How common is trisomy 21?

1/700 births

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What is the level of PAPP-A in the presence of T21?

Decreased

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What is triploidy NOT associated with unlike the other trisomys?

Maternal age

What are the biochemical markers at 1st trimester screen?

- B-hCG | - PAPP-A

Once fertilized how may chromosomes are present in aneuploidy?

45 or 47

What is the most important LESS specific appearance of T18?

Strawberry shaped head

Does maternal age increase the risk of Turners?

No, maternal age is not a factor.

What is turners syndrome?

Missing one of the sex chromosomes (an x or a y from the paternal side) (45xo)

What is Alobar Holoprosencephaly? (4 points)

- Little to no cortical mantle - Single Horseshoe ventricle - Fused thalami - Absent 3rd ventricle and falx

What is the major cause of increased infant mortality in trisomy 21?

Cardiac abnormalities

What is duodenal atresia known as?

"Double bubble"

What substances are tested in the quad screen?

1. AFP 2. uE3 3. B-hCG 4. Inhibit A

Look at the images

...

What is aneuploidy?

"Bad set" - State of having abnormal number of chromosomes (1 extra or 1 less).

What gender are people with Turners and what condition are they all affected by?

All are females and all are sterile

What is the poor prognosis of T18 due to?

Heart and GI defects

What heart defect is common with Turner's?

Coarctation of the aorta

How often are triploidy cases due to a diploid egg?

40 %

What is the specific US appearance of Trisomy 21? (6)

1. Thick nuchal fold 2. Heart defect 3. Mild renal dilation 4. Duodenal atresia 5. Tracheoesophageal fistula 6. Shortened long bones

What is lobar Holoprosencephaly? (2)

- Fused anterior horns that are squared off | - Incomplete falx and 3rd ventricle

How often are triploidy cases fertilized with two sperm?

60%

What is the medical term for mild renal dilation?

Pelviectasis/Pyelectosis

What is the prognosis of T18?

Almost always lethal 50% die in 1st 2 months 95% die in 1st year

How does the prognosis of triplody differ between paternal and maternal?

Paternal = Half will miscarry Maternal = More live births than paternal

What is hypotelorism?

Abnormally close eyes

What is the specific U/S appearance of T18? (6)

- Choroid plexus cysts - Early onset of symmetric IUGR with poly hydramnios - Clenched fists/clinodactyly - Club feet - Rocker bottom feet - Heart defects

What is clinodactyly?

An abnormal

What is uE3?

Unconjugated estriol

How does the hCG levels differ between paternal and maternal triploidy?

Paternal = increased hCG Maternal = low in 2nd trimester due to small placenta

What is semilobar Holoprosencephaly? (4 points)

- Brain mantle present - Single horseshoe ventricle - Incomplete fusion of thalami - Absent falx and 3rd ventricle

What is Microphthalmia?

One or both eyes are abnormally small

What are the 3 classifications of Holoprosencephaly?

1. Lobar 2. Semilobar 3. Alobar

How does IUGR differ between maternal and paternal triploidy?

Paternal = small symmetrical IUGR Maternal = asymmetric IUGR

What are the levels on the triple screen in the presence of T21?

MS-AFP decreased UE3 decreased B hCG increased

What is radial ray syndrome?

Absent radius resulting in clubbed hand

What is Holoprosencephaly?

A severe abnomality that occurs when the forebrain fails to develop into two separate hemispheres

What abnormality is NOT detected with triple screen?

T13

What heart defects are common with Trisomy 21? (4)

- AVSD - VSD - ASD - Echogenic foci in LV or RV

What are the less specific US appearances of T21? (7)

- Cystic hygroma - Non immune hydrops - Clinodactyly - Echogenic bowel - Omphalocele - Mild ventriculomegaly - Sandal foot toes

What is hydrops?

Severe edema of the fetus

How does the placenta differ between maternal and paternal triploidy?

Paternal = Large cystic placenta Maternal = small placenta

What are the U/S appearances of triploidy? (11)

- Holoprosencephaly - Agenesis of the corpus callosum - Meningomyelocele - Arnold Chiari malformation - Ventriculomegaly - Heart defects - Facial clefts - Syndactyly - Club feet - Cystic hygroma - Omphalocele

What is turners syndrome called?

Monosomy

What is the most common live born abnormality?

Trisomy 21 (downs syndrome)

What is coarctation of the aorta?

An abnormal narrowing of the descending aorta (ductus arteriosis area).

What are the less specific sonographic features of T13? (8)

- Polydactyly - Clinodactyly - Club feet - Rocker bottom feet - Cystic hygroma - Severe heart defects - Polycystic kidneys (echogenic kidneys) - Enlarged cisterna magna

What is increased Inhibin suggestive of?

Down syndrome

What eye defects occur with T13?

- Microphthalmia - Hypotelorism - Cyclopia

What bones will be shortened in T21?

Long bones: | Femur and humerus

What is the specific U/S appearance of T13? (6)

- Midline defects (holoprosencephaly) - Cleft lip/palate - Eye defects - Proboscis or absent nose - Omphalocele - Microcephaly/IUGR

What is Triploidy associated with?

Partial molar pregnancy

What are the less specific US appearances of T18? (9)

- Strawb head - Cleft lip/palate - Omphalocele - Diaphragmatic hernia - Single umbilical artery - Radial ray syndrome - Micrognathia - Cystic hygroma - Enlarged cysterna magna

What is proboscis?

Large, elongated nose

What is the occurrence/prognosis of Triploidy?

Rare and usually lethal

How common is T13?

1 in 5000-10000 births

What is triploidy?

Form of polyploidy, complete extra set of chromosomes (69xxy)

What are the specific U/S features of Turner's? (6)

- Cystic Hygroma with septations - Hydrops - Heart defects - Renal agenesis - Horseshoe kidney - Pelvic kidney

What substances are tested with triple screen?

1. MS-AFP 2. B hCG 3. UE3

What are the textbook stats for maternal/paternal triploidy?

Paternal = 90% Maternal = 10%

What is T18 associated with?

Late maternal age

What is trisomy?

One extra complete or partial chromosome (47xy)

What is B-hCG?

Beta human chorionic gonadotropin

What is syndactyly?

When one or more digits are fused

What abnormalities can be detected with triple screen?

T21 and T18

What will be increased in the presence of tracheoesophageal fistula?

Increased AFI

What is the term for triploidy resulting from a diploid egg?

Maternal/digyny

What is the term for triploidy resulting from two sperm?

Paternal/diandry

How common is T18?

1 in every 3000-5000 births

What is euploid?

Means "good set" - Having a normal number of chromosomes.