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OBGYN 1 > C10: Fetal Chromosomal Abnormalities > Flashcards

C10: Fetal Chromosomal Abnormalities Flashcards

1
Q

define aneuploidy

what is the opposite of this term

A

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

-euploid

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2
Q

define trisomy

A

one extra complete or partial chromosome (47 XY)

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3
Q

define triploidy

A

a complete extra set of chromosomes (69 XX)

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4
Q

is triploidy a form of polyploidy

A

yes

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5
Q

what is monosomy-turners syndrome

A

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

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6
Q

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

how many chromo will the fetus have?

A

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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7
Q

whats the most common live born chromo abnormality

A

trisomy 21

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8
Q

whats the most common chromo abnormality among SA fetuses

A

turners syndrome (45 Xo)

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9
Q

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

A

they have lethal results in early pregnancy

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10
Q

whats the major cause of mortality in infancy of T21 babies

A

cardiac abnormalitites

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11
Q

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

A

yes

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12
Q

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

A

60%

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13
Q

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

A
  1. alpha feto protein (AFP)
    - produced by liver
  2. unconjugated estriol (UE)
    - produced by liver and placenta
  3. hCG
    - produced by the placenta
  4. inhibit-A
    - produced by placenta
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14
Q

what element does the triple screen not test for

A

Inhibit A

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15
Q

can T13 be predicted w/ the triple screen

A

no

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16
Q

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

A

AFP decreases

B hCG increases

UE decreases

Inhibit A increases (w/ quad screen)

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17
Q

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

A

AFP decreases

B hCG decreases

UE decreases

Inhibit A no change (w/ quad screen)

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18
Q

what are the common US markers for T21

A

-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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19
Q

what does a tracheoesophageal fistula lead to

A

increased AFI

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20
Q

what are 2 other terms for mild renal dilation

A
  • pelviectasis

- pyelectosis

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21
Q

what is duodenal atresia

A

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

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22
Q

what is EIF and how will they appear on US

A

echogenic intracardiac focus….

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

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23
Q

what are some less specific US markers for T21

A
  • cystic hygroma
  • non immune hydrops
  • clinodactyly
  • echogenic bowel
  • omphalocele
  • mild ventriculomegaly
  • sandal foot
24
Q

what is the definition of hydrops

A

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

25
Q

what is clynodactyly

A

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

26
Q

describe T18/Edward syndrome

what % of these fetuses die in the first 2 month of life, how many in first year of life?

A
  • 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

27
Q

what is the 2nd most common chromo abnormality at birth

A

T18/edward syndrome

28
Q

does the chance of the T18 baby increase w/ LMA

A

yes

29
Q

describe the US appearance of T18

A
  • 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
30
Q

if you identify CPS, what must you show

A

open hands

31
Q

what causes a strawberry shaped head in T18

A

premature closure of skull sutures

32
Q

what does radial ray syndrome (absent radius) cause?

A

clubbed hands

33
Q

what are rocker bottom feet

A

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

34
Q

describe T13/Patau syndrome

A
  • its lethal or has a very poor prognosis
  • severe mental retardation
  • mainly associated w/ midline defects
35
Q

does the chance of the T13 baby increase w/ LMA

A

yes

36
Q

what is the 3rd most common chromo abnormality at birth

A

T13/Patau syndrome

37
Q

does the triple screen detect T13

A

no`

38
Q

describe the common US appearance of T13

A

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
39
Q

what are the 3 classifications of holoprosencephaly for T13

which type is the most common

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

alobar

40
Q

describe alobar T13

A
  • little to no cortical mantle
  • single horseshoe ventricle
  • fused thalami and no 3rd ventricle or falx
  • no hemispheres
41
Q

describe semilobar T13

A
  • single horseshoe shaped ventricle w/ brain mantle

- no 3rd ventricle or falx

42
Q

describe lobar T13

A
  • fused anterior horns that appear square
  • incomplete falx
  • 3rd ventricle present, absent cavum septum pellucidi
43
Q

describe the less common US appearance of T13

A
  • polydactyly
  • clinodactyly
  • club feet
  • rocker bottom feet
44
Q 
describe triploidy (69xxy, 69xyy or 69xxx) 
how does it occur?
A
  • 60% fertilized w/ 2 sperm
  • 40% fertilization of a diploid egg (46 chromo)
  • rare and usually lethal
  • hCG markedly high
  • partial molar preg
45
Q

is triploidy associated w/ LMA

A

no

46
Q

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

A
  • large placenta w/ cysts

- termed a partial mole

47
Q

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

A
  • severe early asymmetrical IUGR
  • oligohydramnios
  • thin placenta
48
Q

describe the US appearance of Triploidy

A
  • holoprosencephaly
  • agenesis of corpus callosum
  • meningomyelocele (herniation of of meninges of spine)
  • facial clefts
  • syndactyly
49
Q

what is anasarca

A

edema

50
Q

describe turner’s syndrome (45 X0)

A
  • missing one sex chromo
  • all female and all sterile
  • missing ovaries
51
Q

what is the most common chromo abnormality in SA

A

turners syndrome

52
Q

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

A

yes

53
Q

what % of turners syndrome babies are aborted

A

95%

54
Q

what are the US findings of turners syndrome

A

-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)
55
Q

which US finding is the most significant for turners syndrome

A

cystic hygroma

56
Q

For which 2 chromosomal abnormalities is LMA not a factor

A

Triploidy and Turner syndrome

OBGYN 1 (24 decks)

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