fetal disorders and prenatal diagnosis

Question 1

what are the three classifications of fetal disoreders?

Answer 1

chromosomal
structural
immune

Question 2

what are the numerical chromosomal disorders?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

turner syndrome (45 X)

Question 5

what is the most common chromosomal disorder with living outcomes ?

Answer 5

down syndrome ( trisomy 21)

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

how can we make a diagnosis of Down Syndrome ?

Answer 9

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

Question 10

what are the risk factors for neural tube defects ?

Answer 10

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

Question 11

what can NTD be classified into ?

Answer 11

open and closed

Question 12

what is hydrocephalus ?

Answer 12

excessive accumulation of CSF in the brain

Question 13

what is the harmful effect of hydrocephalus ?

Answer 13

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

Question 14

what is the most common cause of hydrocephalus ?

Answer 14

gene mutation

Question 15

what are the symptoms of hydrocephalus ?

Answer 15

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

Question 16

what is the treatment for hydrocephalus ?

Answer 16

shunt operation to release excess CSF

Question 17

what is anencephaly ?

Answer 17

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

Question 18

what is the prognosis of a baby with anencephaly ?

Answer 18

baby will only live for a few hours after birth

Question 19

where are the most commonn spinal defects found ?

Answer 19

lumbar ans sacral bifida

Question 20

what are the types of spinal defects ?

Answer 20

spina bifida occulta
meningocele
myelomeningocele

Question 21

at what time during pregnancies fo fetal anomalies happen ?

Answer 21

during the first trimester when organogenesis happens

Question 22

what is the treatment for spinal defect ?

Answer 22

surgical correction

Question 23

what are cleft and lip palate?

Answer 23

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

Question 24

what are the type of abdominal wall defects ?

Answer 24

omphalocele

gastroschisis

Question 25

what is the difference betweenn omphalocele and gastroschisis ?

Answer 25

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

Question 26

what causes mortality in cases of omphalocele ?

Answer 26

cardiac defects

Question 27

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

Answer 27

Rh incompatibility

Question 28

what is Rh incompatibility ?

Answer 28

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

Question 29

what are the causes of Rh incompatibility ?

Answer 29

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

Question 30

what is congenital haemolytic anemia ?

Answer 30

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

Question 31

what is icterus gravis neonatorum ?

Answer 31

the commonest and the moderate form | the baby is delivered anemic but will only begin to appear jaundiced after labour by 24 hours

Question 32

what is kernicterus ?

Answer 32

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

Question 33

what is hydrops fetalis ?

Answer 33

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

Question 34

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

Answer 34

buddha sign

Question 35

what does prenatal screenning include ?

Answer 35

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

Question 36

what are the maternal serum biochemical markers ?

Answer 36

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

Question 37

what is the double marker test ?

Answer 37

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

Question 38

when is the double marker test performed ?

Answer 38

at 11-13 weeks ( first trimesteric)

Question 39

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

Answer 39

high HCG and low PAPP-A levels

Question 40

what is the triple marker test ?

Answer 40

the combination of AFP, HCG and UE3 in one test

Question 41

when is triple marker test performed ?

Answer 41

in the second trimester at 15-16 weeks

Question 42

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

Answer 42

HCG high AFP low UE3 low

Question 43

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

Answer 43

all three markers would be low

Question 44

in neural tube defects which maternal marker will be raised ?

Answer 44

AFP

Question 45

when are the anomaly scans performed ?

Answer 45

1st trimesteric ultrasound ( 11-13 weeks) | 2nd ( 18-22 weeks)

Question 46

what ultrasonography findings could indicate down syndrome ?

Answer 46

nose hypoplasia | NT >3 mm

Question 47

when can cell free foetal DNA be used ?

Answer 47

using PCR at around 10-12 weeks gestation

Question 48

what is chorionic villous sampling ?

Answer 48

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

Question 49

what is the risk of CVS ?

Answer 49

2% risk of miscarriage

Question 50

when can amniocentesis be performed ?

Answer 50

14-16 weeks

Question 51

what are the risks of amniocentesis ?

Answer 51

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

Question 52

what is cordocenteses ?

Answer 52

obtaining fetal blood sample

Question 53

when can cordiocentesis be done ?

Answer 53

20 weeks gestation

Question 54

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

Answer 54

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