Module 10: Fetal Chromosome abnormalities Flashcards
What is an euploid?
A normal number of chromosomes- Means good set
What does aneuploidy means?
State of having an abnormal number of chromosomes (1 extra or 1 less) means bad set
What does trisomy means?
One extra complete or partial chromosome present in the cell (47xy)
What does triploidy mean?
A complete extra set of chromosomes resulting in 3 complete chromosome sets per cell (69xxy) (a form of polyploidy)
What does monosomy - turners syndrome means?
45xo - missing an x or y from paternal side (sperm)
What is a karyotype? How is it described?
- Chromosome set of an individual
- Described in terms of both the number of structure of chromosomes
In total there are how many chromosomes?
46, 23 from either parent
What is the normal karyotype? for each gender?
Female - 46 xx
Male 46 xy
What is an aneuploidy? How can this happen?
- State of having an abnormal number of chromosomes (1 extra or 1 less)
- A chromosome pair fails to separate during meiosis
The meiotic error that causes aneuploidy is called what?
Non disjunction
How does Aneuploidy happen? 2
- The sperm or oocyte has 2 copies of a particular chromosome or no copies instead of one copy in haploid state
- Once fertilization occurs the zygote either has 45, 47 chromosomes rather than 46
Approx how many live born infants has a chromosome abnormality?
1 in 160
Most common live chromosome abnormality is what? How many are afflicted?
trisomy 21 (down syndrome) 1 in 800 births
Most common chromosome abnormality among spontaneous aborted fetuses is what?
Turners syndrome (45xo)
Trisomy 18 and 13 are more severe than what?
Trisomy 21
Other autosomal trisomies are seen how frequently? And why?
Rarely due to lethal result and early pregnancy loss
What increases the risk of having a baby with down syndrome?
Late maternal age (over 35)
Is down syndrome lethal?
NO
Maternal serum triple or quad screen is what rate for down syndrome?
60%
What is the major cause of increased mortality in down syndrome?
Cardiac abnormalities
What are some things seen from down syndromes?
Intellectual disabilities and developmental delays (vary by individual)
What are some maternal blood test elements? 4
- AFP
- EU
- hCG
- Inhibin - A
What is AFP used for? What does it stand for? Where is it produced?
- Maternal blood test
- Alpha fetoprotein
- Produced by fetal liver
What is EU used for? Where is it produced? What days it stand for?
- Maternal blood test elements
- Produced by fetal liver and placenta
- unconjugated estriol
What is hCG used for in testing? What does it stand for? Where is it produced?
- Maternal blood test element
- Human chorionic gonadotropin
- Produced by the placenta
What is Inhibin- A? Where is it produced?
- Maternal blood test element
- hormone produced by the placenta
What are some triple screen maternal blood test results seen in trisomy 21?
- MS AFP decreased
- B hCG increaesd
- UE decreased
What are some triple screen maternal blood test results seen on trisomy 18?
- MSAFP decrease
- B hCG decrease
- UE3 Decrease
Is trisomy 13 predicted with triple screen maternal blood test?
Not predicted with the triple screen
What is looked for on a triple screen blood test?
- Alpha fetoprotein
- Human chorionic gonadotropin
- Estriol
What is the results of quad screen maternal test for trisomy 21?
- MSAFP decrease
- B hHCG increase
- UE3 Decrease
- Inhibin A increase
What are the results of Trisomy 18 maternal blood test quad screen?
- MSAFP Decrease
- B hCG decrease
- UE3 Decrease
- Inhibin A no change
What are some trisomy 21: sonographic appearances? 7
- Thick nuchal fold
- Absent or hypoplastic nasal bone
- Heart defects
- Mild renal dilation
- Duodenal artresia
- Tracheoesophageal fistual (increased AFI)
- Shortened long bones
thatdms
What are some heart defects for trisomy 21? 3
- AVSD
- VSD or ASD
- Echogenic focus in left or right ventricle
What are mild renal dilation seen in Trisomy 21? What is the size?
- Pelviectasis also called pyelectosis
- > 5mm
What are some less specific sonographic appearances in trisomy 21? 7
- Cystic hygroma
- Non immune hydrops
- Clinodactyly
- Echogenic bowel
- Omphalocele
- Mild ventriculomegaly- lateral cerebral ventricles
- Sandal foot
Some CNC
What is the lethality of trisomy 18?
Almost always lethal or very poor prognosis
What are the stats for survival for trisomy 18?
- 50% die in 1st two months of life
- 90% die in 1st year of life
What are some defects that trisomy 18 portray throughout life?
Profound intellectual disability
Why is the diagnosis so poor for trisomy 18?
Heart and GI abnormalities
What is the 2nd most common chromosome abnormality at birth?
Trisomy 18
What is another name for trisomy 18?
Edwards syndrome
What is the occurrence rate of trisomy 18?
1 in every 3000 to 5000 births
What increases Trisomy 18?
LMA
What does the triple screen markers look like for Trisomy 18?
All markers are low
What does trisomy 18 look like sonographically? 5
- Early onset of symmetric IUGR with polyhydramnios
- Clenched fists and/or clinodactyly
- Club feet and/or rocker bottom feet
- CPC’s
- Heart defects (large VSD most common)
Note: if CPC are identified, open hands must be demonstrated
ccche
What are some less specific sonographic appearances to T18? 9
- Cleft lip and/or palate
- Omphalocele
- Diaphragmatic hernia
- Single umbilical artery
- Strawberry shaped head
- Radial ray syndrome (absent radius)
- Micrognathia
- Cystic hygroma
- enlarged cisterna magna
some drs. CC
Is trisomy 13 lethal?
Lethal or very poor prognosis
What is another name for trisomy 13?
Patau syndrome
What is the survivability of trisomy 13 at birth and in the first year?
70% are stillborn, and 85% die in the 1st year
Survivors of trisomy 13 have what kind of traits?
Profound intellectual disability
What is the 3rd most common chromosome abnormality seen at birth?
Trisomy 13 or patau syndrome
What is the occurance rate of trisomy 13?
1 in 5000 to 10,000 births
What increases the risk of trisomy 13?
Advanced maternal age
Does triple screen test detect trisomy 13?
no
What is the midline sonographic defects of trisomy 13? What kind of abnormality is it? What is it fusion of? What are the classifications?
Holoprosencephaly
1. Severe abnormality of the forebrain cleavage (cerebrum or prosencephalon)
2. Fusion of the cerebral hemispheres and thalami
3. 3 classifications (lobar(mild), semilobar, alobar (severe))
What does Holoprosencephaly lobar look like? 2
- Fused anterior horns that are off
- incomplete falx but 3rd ventricle may be seen
What does holoprosencephaly semi lobar look like? 2
- Single horseshoe shaped ventricle with brain mantle
- No 3rd ventricle or falx
What does holoprosencephaly alobar look like? 3
- Little or no cortical mantle
- Single horseshoe shaped ventricle
- Fused thalami and no 3rd ventricle or falx
What are some non midline features of Trisomy 13? 7
- Cleft lip and/or palate
- Microphthalmia
- Hypotelorism
- Cyclopia
- Absent nose or replaced by proboscis
- Omphalocele
- Microcephaly or IUGR
Coma HMC
What are some less specific sonographic features of Trisomy 13? 8
- Polydactyly - extra fingers
- Clinodactyly
- Club feet
- Rocker bottom feet
- Cystic hygroma
- Severe heart defects such as hypoplastic left heart or VSD
- Polycystic kidneys (echogenic kidneys)
- Enlarged cisterna magna
C spec CPR
Where can the extra set of triploidy come from
Extra set can come from either parent
1. 60% fertilized with 2 sperm
2. 40% fertilization of diploid (46 chromosomes) egg
What is the lethality and occurrence rate of Triploidy?
Rare Rate and usually lethal
What are some markers on the triple/ quad screen that would indicate triploidy?
hCG marketed high (8x normal)
What might happen with triploidy? (In terms of pregnancy)
Partial molar pregnancy
Is triploidy associated with maternal age?
No
What is the karyotype for triploidy?
69xxy, 69 xyy, 69xxx
What is the sonographic appearance of triploidy? What happens when mother contributes extra chromosomes? What happens early on in the pregnancy?
- Large placenta with cysts
- Thin placenta when mother contributes the extra chromosomes
- Severe early asymmetric IUGR and oligohydramnios
What is a partial mole? How are they formed?
- Large placenta with cysts
- One when fertilized with two sperm (paternal)
What are some general sonographic 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
Ham as focc vh
What is turners syndrome 45xo? What are the gender of the babies? What is the fertility like for these children?
- When one of the sex chromosomes are missing
- All are female
- The children are all sterile - missing ovaries
Does maternal age affect the occurrence rate of turners syndrome?
Nope
What is the most common chromosome abnormality in spontaneous abortions? What is the occurrence rate for therapeutic aboriton
- turners syndrome 45xo
- 95% undergo therapeutic abortion
Is there any life threatening anomalies to Turner’s?
Few and normal intellect
What are some sonographic appearances of turners syndrome? 4
- Cystic hygroma
- Hydrops
- Heart defects
- Renal abnormalities
CHHR
What cystic hygromas seen in turners syndrome look like? 2
- Septated cystic collections within the fluid at the back of the neck
- Web neck
What are some heart defects seen in turners syndrome?
Coarctation of the aorta
What are the renal abnormalities of Turners? 3
- Agenesis
- Horseshoe kidney
- Pelvic kidney
What is this an image of?
Duodenal atresia
What does this image demonstrate?
Bilateral EIF (echogenic intracardiac focus)
What do these images represent?
The thickened nuchal fold of trisomy 21
What do these images represent?
Hydrops: a condition in which large amounts of fluid build up in a baby’s tissues and organs, causing extensive swelling (edema)
What do these images represent?
Clinodactyly: your child has a finger that curves to one side. It usually affects the little (pinky) finger but can affect other fingers as well.
What do these images represent?
- Sandal gap: A widely spaced gap between the first toe (the great toe) and the second toe
- Cystic hygroma: a birth defect that appears as a sac-like structure with a thin wall that most commonly occurs in the head and neck area of an infant
What does this image demonstrate?
All the common sonographic appearances with T21
What is the significance of these images?
The open and clenched fists are a common sign of trisomy 18
What do these images represent?
Club feet + rocker bottom
What does these images represent?
Strawberry headshape
What does this image demonstrate?
All the common sonographic features of T18
What does this image demonstrate?
Holoprosencephaly in degree of severity
What does this image represent?
Lobar Holoprosencephaly
What do these images represent?
Holoprosencephaly + cleft lip
What does this image demonstrate?
Proboscis and cyclopia (note the nose on the forehead)
What does this image demonstrate?
Trisomy 13 common sonographic features
What does this image represent?
Symmetrical IUGR and and normal fetus
What does this image represent?
Cystic hygroma
