Module 6: Chromosomal Abnormalities Flashcards
What is the most common abnormality among spontaneously aborted fetuses?
Turner’s (45xo)
95% are aborted
What is non-disjunction?
The meiotic error that causes aneuploidy where a chromosome pair fails to separate during meiosis.
What is the value of mild renal dilation?
Greater than or equal to 5mm
What is the prognosis of T13?
Lethal/poor
70% are still born
85% die in 1st year
Survivors = profound mental retardation
What is another name for T18?
Edward syndrome
What heart defects are seen with T13?
- VSD
- Hypoplastic left heart
What are the levels on the triple screen in the presence of T18?
MS-AFP decreased
uE3 decreased
B hCG decreased
(All decreased)
What heart defect is most common in T18?
Large VSD
What is PAPP-A?
Pregnancy Associated Plasma Protein A
Why are autosomal trisomies rarely seen?
Lethal (SA)
How can clinodactyly be identified on U/S?
Overlapping digits in fist
What is another name for T13?
Patau syndrome
What is the triple screen detection rate of trisomy 21?
60%
What is the prognosis of Turners babies that survive birth?
Few life threatening anomalies and normal intellect
What increases the risk of T13?
Advanced maternal age
How often do chromosomal abnormalities occur?
1/160 live births
What increases the risk of trisomy 21?
Maternal age
What is a marker for Triploidy?
Markedly high BhCG (8x higher than normal)
What is Micrognathia?
Underdeveloped jaw
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.
What is Cystic hygroma?
Multiple cysts in lymphatic system
What is the 2nd most common chromosome abnormality at birth?
T18/Edwards
How common is trisomy 21?
1/700 births
What is the level of PAPP-A in the presence of T21?
Decreased
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?
- AFP
- uE3
- B-hCG
- 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)
- Thick nuchal fold
- Heart defect
- Mild renal dilation
- Duodenal atresia
- Tracheoesophageal fistula
- 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?
- Lobar
- Semilobar
- 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?
- MS-AFP
- B hCG
- 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.
