Module 10 : Fetal Chromosomal Abnormalities Flashcards Preview

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Flashcards in Module 10 : Fetal Chromosomal Abnormalities Deck (34)
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1

aneuploidy - définition

- state of having an abnormal number of chromosomes (1 extra or 1 less)
+ means bad set

2

euploidy

- means good set

3

trisomy

- one extra complete or partial chromosome (47XY)
- 21, 18, 13

4

triploidy

- a complete extra set of chromosomes (69 XXY)
- form of polyploidy

5

monosomy turners syndrome

- 45Xo
- missing an X or Y from paternal (fathers) side
- always female

6

aneuploidy

- meiotic error that causes aneuploidy is call non disjunction
- chromosome pair fails to separate during meiosis
+ the sperm of oocyte has 2 copies of particular chromosome or no copies instead of one copy in haploid state
- once fertilization occurs in zygote wither has 45 or 47 chromosomes rather than 46

7

chromosome abnormalities

- 1/160 live born infants has a chromosome abnormalities
- most common LIVE born chromosome abnormality is trisomy 21
- most common chromosome abnormality among spontaneously aborted fetus is turners
- trisomy 18 and 13 more severe than trisomy 21
- other trisomies rarely seen with lethal result

8

trisomy 21

- cardiac abnormalities are the major cause of increased mortality in infancy
- decreased intelligence
+ severity varies
- increased risk of down syndrome with late maternal age
- not considered lethal
- maternal serum prenatal screen second trimester or quad screen 60% detection rate

9

quad screen elements

- AFP
-EU
-hCG
- Inhibin A

10

AFP

- alpha-fetoprotein
- produced by fetal liver

11

EU

- unconjugated estriol
- produced by fetal liver and placenta

12

hCG

- human chorionic gonadotropin
- produced by the placenta

13

Inhibin A

- hormone produced by the placenta

14

triple screen - trisomy 21

- MSAFP decreases
- B hCG increases
- UE3 decreases
- inhibit A increases

15

triple screen - trisomy 18

- MSAFP decreases
- B hCG decreases
- UE3 decreases
- inhibin A doesnt change

16

triple screen - trisomy 13

- not predicted with quad screen

17

trisomy 21 sonographic appearance

- thick nuchal fold > 6mm
- heart defects
+ AVSD
+ VSD or ASD
+ echogenic focus in left or right ventricle
- mild renal dilation
+ pelviectasis also called pyelectosis
+ >/= 5 mm
- duodenal atresia (double bubble)
- tracheoesophageal fistula (increased FI)
- shortened long bones (femur and humorous)

18

less specific sonographic appearence trisomy 21

- cystic hygroma = fluid back of babies neck
- non immune hydros = fluid in cavities
- clinodactyly = crooked fingers
- echogenic bowel = same as heart
- omphalocele
- mild ventriculomegaly
- sandal foot

19

trisomy 18

- Edwards syndrome
- almost always lethal or very poor prognosis
- 50% die in first two months
- 90% die in first year
- survivors have profound mental retardation
- poor prognosis due to heart GI abnormalities
- second most common at births
- increases with LMA
- triple screen markers all low

20

trisomy 18 sonographic appearance

- early onset of symmetric IUGR with polyhydroamnious
- clenched fists and or clinodactyly
- club feet or rocker bottom feet
- CPCs - choroid plexus cysts
- heart defects
+ large VSD most common
* if CPCs are identified open hands need to be indentified

21

trisomy 18 less specific signs

- cleft lip or palate
- omphalocele
- diaphragmatic hernia
- single umbilical artery
- strawberry shaped head
- radial ray syndrome (absent radius)
- micrognathia (receding chin)
- cystic hygroma
- enlarged cisterna magna

22

trisomy 13

- patau syndrome
- 70% are still born 85% die in first year
- survivors have profound mental retardation
- 3rd most common
- increased risk with advanced maternal age
- triple screen dos not detect trisomy 13

23

T 13 sonographic appearance

-holoprosencephaly
+ severe abnormality of fore brain cleavage (cerebrum or prosencephalon)
+ fusion of cerebral hemispheres and thalami
+ 3 classifications
= lobar - mild
= semilobar
= lobar - severe

24

lobar - holoprosencephaly

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

25

semilobar - holoprosencephaly

- single horseshoe shaped ventricle with brain mantle
- no 3rd ventricle or falx

26

lobar - holoprosencephaly

- fused anterior horns that are squared off
- incomplete falx but 3rd ventricle may be seen

27

T 13 more sonographic signs

- cleft lip or palate
- micropthalmia
- hypotelorism
- cyclopia
- absent nose or replaced by proboscis
- omphalocele
- microcephaly or IUGR

28

T 13 less specific indicators

- polydactyly
- clinodactyly
- club feet
- rocker bottom feet
- cystic hygroma
- severe heart defects
+ hypo plastic left heart
+ VSD
- polycystic kidneys (echogenic kidneys)
- enlarged cisterna magna

29

triploidy

- 69xxy 69xyy 69xxx
- 60% fertilized with 2 sperm
- 40% fertilization of a diploid (46 chromosome egg)
- rare and usually lethal
- hCG marked high (8x normal)
- partial molar pregnancy
- not associated with maternal age

30

triploidy sonographic appearance

- large placenta with cysts
+ only when fertilized with 2 sperm
+ termed partial mole
- thin placenta when mother contributes the extra chromosomes
- severest asymmetric IUGR and oligohydroamnios