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