C10: Fetal Chromosomal Abnormalities Flashcards by M B

define aneuploidy

what is the opposite of this term

the state of having an abnormal number of chromosomes…means a bad set

-euploid

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define trisomy

one extra complete or partial chromosome (47 XY)

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define triploidy

a complete extra set of chromosomes (69 XX)

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is triploidy a form of polyploidy

yes

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what is monosomy-turners syndrome

-an individual is missing an X or Y from the paternal side
(45 Xo)
-will always be female

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what is the name of the meiotic error that causes aneuploidy and describe how it happens.

how many chromo will the fetus have?

non-disjunction: when a chromo pair fails to separate during meiosis and the sperm or egg has 2 copies of a chromo or no copies, instead of one copy

-45 or 47 instead of 46

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whats the most common live born chromo abnormality

trisomy 21

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whats the most common chromo abnormality among SA fetuses

turners syndrome (45 Xo)

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why are trisomy’s other than 21, 13 and 18 not commonly seen

they have lethal results in early pregnancy

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whats the major cause of mortality in infancy of T21 babies

cardiac abnormalitites

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does the risk of a T21 baby increase w/ late maternal age

yes

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what is the detection rate of T21 w/ a maternal serum prenatal screen (@ 16 wks) or Quad screen

60%

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what are the 4 maternal blood test elements and where are they produced

alpha feto protein (AFP)
- produced by liver
unconjugated estriol (UE)
- produced by liver and placenta
hCG
- produced by the placenta
inhibit-A
- produced by placenta

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what element does the triple screen not test for

Inhibit A

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can T13 be predicted w/ the triple screen

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w/ T21, how do the maternal blood test elements change w/ the triple screen and quad screen

AFP decreases

B hCG increases

UE decreases

Inhibit A increases (w/ quad screen)

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w/ T18, how do the maternal blood test elements change w/ the triple screen and quad screen

AFP decreases

B hCG decreases

UE decreases

Inhibit A no change (w/ quad screen)

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what are the common US markers for T21

-thick nuchal fold (>6mm)

-heart defects
+ AVSD/endocardial cushion defect, VSD, ASD, EIF)

-mild renal dilation
+ >/= 5 mm

duodenal atresia
tracheoesophageal fistula
shortened long bones (femur and humerus)
hypoplastic nasal bone

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what does a tracheoesophageal fistula lead to

increased AFI

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what are 2 other terms for mild renal dilation

pelviectasis

- pyelectosis

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what is duodenal atresia

caused by an area of the duodenum thats been restricted and narrowed so bubbles out

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what is EIF and how will they appear on US

echogenic intracardiac focus….

-cause by calcifications of the pap muscles and will be more echogenic than bone

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what are some less specific US markers for T21

cystic hygroma
non immune hydrops
clinodactyly
echogenic bowel
omphalocele
mild ventriculomegaly
sandal foot

what is the definition of hydrops

-fluid in a least 2 body cavities or 1 body cavity w/ edema

what is clynodactyly

3rd bone in the pinky finger is missing and finger is crooked

describe T18/Edward syndrome what % of these fetuses die in the first 2 month of life, how many in first year of life?

- almost always lethal or very poor prognosis - profound mental retardation - cardiac and GI abnormalities +majority of babes die in first months of life of first year

what is the 2nd most common chromo abnormality at birth

T18/edward syndrome

does the chance of the T18 baby increase w/ LMA

yes

describe the US appearance of T18

- early symmetric IUGR w/ polyhydramnios - clenched fists or/and clinodactyly - club feet and/or rocker bottom feet - CPCs - heart defects (lg VSD is common) - strawberry shaped head

if you identify CPS, what must you show

open hands

what causes a strawberry shaped head in T18

premature closure of skull sutures

what does radial ray syndrome (absent radius) cause?

clubbed hands

what are rocker bottom feet

when the bottom of the feet curve out and theres no arch

describe T13/Patau syndrome

- its lethal or has a very poor prognosis - severe mental retardation - mainly associated w/ midline defects

does the chance of the T13 baby increase w/ LMA

yes

what is the 3rd most common chromo abnormality at birth

T13/Patau syndrome

does the triple screen detect T13

no`

describe the common US appearance of T13

characterized by midline defects: -holoprosencephaly +severe abnormality of the forebrain cleavage... specifically the cerebrum and prosencephalon +fusion of cerebral hemispheres and thalami - cleft lip and/or palate - microphthalimia - hypotelorism - microcephaly or IUGR

what are the 3 classifications of holoprosencephaly for T13 which type is the most common

1. Lobar - mild 2. Semilobar 3. Alobar - severe alobar

describe alobar T13

- little to no cortical mantle - single horseshoe ventricle - fused thalami and no 3rd ventricle or falx - no hemispheres

describe semilobar T13

- single horseshoe shaped ventricle w/ brain mantle | - no 3rd ventricle or falx

describe lobar T13

- fused anterior horns that appear square - incomplete falx - 3rd ventricle present, absent cavum septum pellucidi

describe the less common US appearance of T13

- polydactyly - clinodactyly - club feet - rocker bottom feet

``` describe triploidy (69xxy, 69xyy or 69xxx) how does it occur? ```

- 60% fertilized w/ 2 sperm - 40% fertilization of a diploid egg (46 chromo) - rare and usually lethal - hCG markedly high - partial molar preg

is triploidy associated w/ LMA

describe the US appearance of triploidly when fertilized w/ 2 sperm

- large placenta w/ cysts | - termed a partial mole

describe the US appearance of triploidly when mom contributes the extra chromosome

- severe early asymmetrical IUGR - oligohydramnios - thin placenta

describe the US appearance of Triploidy

- holoprosencephaly - agenesis of corpus callosum - meningomyelocele (herniation of of meninges of spine) - facial clefts - syndactyly

what is anasarca

edema

describe turner's syndrome (45 X0)

- missing one sex chromo - all female and all sterile - missing ovaries

what is the most common chromo abnormality in SA

turners syndrome

do turners syndrome babies have few life threatening anomalies and normal intellect

yes

what % of turners syndrome babies are aborted

95%

what are the US findings of turners syndrome

-cystic hygroma (bilaterally) + separations w/in the fluid at the back of the neck + web neck - hydrops - heart defects (coarctation of the AO) - renal abnormalities (agenesis, horseshoe or pelvic kidney)

which US finding is the most significant for turners syndrome

cystic hygroma

For which 2 chromosomal abnormalities is LMA not a factor

Triploidy and Turner syndrome