fetal disorders and prenatal diagnosis Flashcards

1
Q

what are the three classifications of fetal disoreders?

A

chromosomal
structural
immune

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2
Q

what are the numerical chromosomal disorders?

A

fetus has an extra chromosome
or
the fetus has a missing chromosome

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3
Q

what are the chromosomal fetal disorders which have a nextra chromosome ?

A
down syndrome ( trisomy 21)
Edwards syndrome ( trisomy 18)
patau syndrome ( trisomy 13)
klinfelter syndrome ( 47 XXY)
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4
Q

what are the fetal disorders in which there is a missing chromosome ?

A

turner syndrome (45 X)

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5
Q

what is the most common chromosomal disorder with living outcomes ?

A

down syndrome ( trisomy 21)

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6
Q

what are the risk factors of birthing a baby with down syndrome ?

A

maternal age above 35
previous children with down syndrome
parent with a translocated gene

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7
Q

what are the physical features of a child with down syndrome ?

A
excess skin at the nape of the neck 
separated joints 
small ears 
small mouth 
white spots on the coloured part of the eye : Brush-field spots
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8
Q

what are the more specific features of babies with down syndrome ?

A
eyes that slant up at the outer corner 
small ears 
flat noses 
short neck 
most patients have cardiac anomalies
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9
Q

how can we make a diagnosis of Down Syndrome ?

A
  1. first an ultrasound needs to be made , looking for the thickness of the nuchal translucency , give that it is more than 3 mm there is a higher susceptibility of down syndrome
  2. double and triple marker test can be performed
  3. NIPT ( non invasive prenatal testing) can also be used for screening
    but to make a final diagnosis of down syndrome , genetic testing must be performed
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10
Q

what are the risk factors for neural tube defects ?

A
low serum folate concentration 
specific drugs such as antiepileptic drugs 
positive family history 
diabetic mothers 
high body temperature 
obesity
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11
Q

what can NTD be classified into ?

A

open and closed

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12
Q

what is hydrocephalus ?

A

excessive accumulation of CSF in the brain

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13
Q

what is the harmful effect of hydrocephalus ?

A

excessive fluid causes an abnormal widening of spaces in the brain called ventriculomegalia creating a harmful pressure on the brain

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14
Q

what is the most common cause of hydrocephalus ?

A

gene mutation

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15
Q

what are the symptoms of hydrocephalus ?

A
large head with a transparent scalp 
bulging forehead 
seizures 
visual problems 
abnormal reflexes
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16
Q

what is the treatment for hydrocephalus ?

A

shunt operation to release excess CSF

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17
Q

what is anencephaly ?

A

when the skull, scalp and the brain dont form properly in the womb

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18
Q

what is the prognosis of a baby with anencephaly ?

A

baby will only live for a few hours after birth

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19
Q

where are the most commonn spinal defects found ?

A

lumbar ans sacral bifida

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20
Q

what are the types of spinal defects ?

A

spina bifida occulta
meningocele
myelomeningocele

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21
Q

at what time during pregnancies fo fetal anomalies happen ?

A

during the first trimester when organogenesis happens

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22
Q

what is the treatment for spinal defect ?

A

surgical correction

23
Q

what are cleft and lip palate?

A

openings or splits in the upper lip, the roof of the mouth or both

24
Q

what are the type of abdominal wall defects ?

A

omphalocele

gastroschisis

25
Q

what is the difference betweenn omphalocele and gastroschisis ?

A
  1. omphalocele the gut presents inside a sac and straight from the umbilicus
  2. there is no sac in gastroschisis and the exit is next to the umbilicus
26
Q

what causes mortality in cases of omphalocele ?

A

cardiac defects

27
Q

what is the most common and most important fetal immune disorder ?

A

Rh incompatibility

28
Q

what is Rh incompatibility ?

A

it is an excessive haemolysis of fetal RBCs by antibodies that pass through the placenta from maternal blood

29
Q

what are the causes of Rh incompatibility ?

A
  1. rh alloimmunization of an Rh -ve mother with a Rh +ve husband and so having a Rh +ve baby
  2. sensitization from previous delivery or miscarriage without receiving an anti D injection
  3. previous transfusion of an Rh+ve blood
30
Q

what is congenital haemolytic anemia ?

A

mildest form which results in fetal anemia that develops 2 weeks after birth also called erythroblastosis fetalis

31
Q

what is icterus gravis neonatorum ?

A

the commonest and the moderate form

the baby is delivered anemic but will only begin to appear jaundiced after labour by 24 hours

32
Q

what is kernicterus ?

A

this develops when the foetal bilirubin level exceeds 20mg as bilirubin crosses the blood brain barrier and becomes deposited in the basal ganglia , which may cause neonatal death

33
Q

what is hydrops fetalis ?

A

intrauterine fetal death occurring due to severe hemolytic anemia that leads to heart failure

34
Q

what sign is seen in ultrasound that may indicate hydrops fetalis ?

A

buddha sign

35
Q

what does prenatal screenning include ?

A
  1. Rh factor
  2. indirect coombs test
  3. maternal serum biochemical markers
  4. US screening for nuchal translucency
  5. cell free fetal DNA
36
Q

what are the maternal serum biochemical markers ?

A

AFP : alpha fetoprotein which is produced by the yolk sac, fetal liver and GIT
HCG
PAPP-A : pregnancy associated plasma protein A
UE3: unconjugated estriol

37
Q

what is the double marker test ?

A

testing for both HCG and PAPP-A together with the ultrasound measurement of the nuchal translucency

38
Q

when is the double marker test performed ?

A

at 11-13 weeks ( first trimesteric)

39
Q

what would be the results of the double marker test for a baby with down syndrome ?

A

high HCG and low PAPP-A levels

40
Q

what is the triple marker test ?

A

the combination of AFP, HCG and UE3 in one test

41
Q

when is triple marker test performed ?

A

in the second trimester at 15-16 weeks

42
Q

what test results in the triple marker test would show a high risk of down syndrome ?

A

HCG high
AFP low
UE3 low

43
Q

what would the maternal marker levels be like in trisomy 18 ?

A

all three markers would be low

44
Q

in neural tube defects which maternal marker will be raised ?

A

AFP

45
Q

when are the anomaly scans performed ?

A

1st trimesteric ultrasound ( 11-13 weeks)

2nd ( 18-22 weeks)

46
Q

what ultrasonography findings could indicate down syndrome ?

A

nose hypoplasia

NT >3 mm

47
Q

when can cell free foetal DNA be used ?

A

using PCR at around 10-12 weeks gestation

48
Q

what is chorionic villous sampling ?

A

a sample of the placenta is used ( from trophoblastic cells) , this sample can be obtained either trans-abdominal or trans-vaginal , this can be done as early as 11 weeks

49
Q

what is the risk of CVS ?

A

2% risk of miscarriage

50
Q

when can amniocentesis be performed ?

A

14-16 weeks

51
Q

what are the risks of amniocentesis ?

A

small risk of fetal miscarriage
small risk of fetal infection n
rupture of membranes
accidental haemorrhage

52
Q

what is cordocenteses ?

A

obtaining fetal blood sample

53
Q

when can cordiocentesis be done ?

A

20 weeks gestation

54
Q

what is the earliest form of testing that can be done in an effort to detect chromosomal abnormalities ?

A

pre implantation genetic diagnosis when a cell is taken at the 8 cell stage without any subsequent complications to the fetus