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Transfusion Science > Haemolytic Disease of the Newborn and Foetus > Flashcards

Haemolytic Disease of the Newborn and Foetus Flashcards

1
Q

What is Haemolytic Disease of the Newborn and Foetus

A

A condition in which the life span of foetal red cells is reduced by the action of specific antibodies derived from the mother by placental transfer.

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2
Q

What led to a dramatic decrease in HDN cases after the 1970s

A
  • Routine antenatal care including:
  • screening of all expectant mothers to find those whose pregnancy may be at risk of HDN
  • giving preventative tx accordingly
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2
Q

The disease involves (3)

A
  1. Maternal alloimmunisation -> produces antibody
  2. Transplacental passage of IgG antibody to the foetus
  3. Sensitisation and destruction of foetal cells
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3
Q

What type of immune system do newborns have

A

Primitive immune system

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4
Q

What keeps the foetus alive while they have their primitive immune system

A

The transport of the mothers antibodies across the placenta and into the fetal circulation. This occurs as their immune system matures.

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5
Q

What is a major cause of HDN

A

An incompatibility of the Rh blood group between the mother and foetus

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6
Q

Which pregnancies are at risk of HDN

A

Ones in which a Rd D- mother becomes preggers with a Rh D+ foetus (child inherited D+ antigen from father)

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7
Q

What is the Rh D- mother’s immune response to a Rh D+ foetus

A

The mothers immune response to the fetal D antigens is to form anti D antibodies against it

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8
Q

What type of antibodies are tha anti D antibodies and what does this mean

A

IgG antibodies. These type of antibodies can cross the placenta and be delivered to the fetal circulation.

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9
Q

Why is ABO incompatibility less severe than Rh incompatibility

A

Fetal rbcs express less of the ABO blood group antigens compared with adult levels

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10
Q

When may some foetal cells pass into the maternal blood system (2)

A
  1. At delivery
  2. Occasionally during pregnancy
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11
Q

Initially, what type of antibody is the maternal anti D antibody and can it cross the placenta

A

Initially, the anti D antibody is of the IgM type, this cannot cross the placenta

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11
Q

What happens in subsequent pregnancies after the formation of the IgM anti D antibodies

A

A repeat pregnancy with a Rh D+ child stimulates the rapid production of type IgG anti D antibodies which can cross the placenta into the foetal circulation

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12
Q

Once in foetal circulation what does the anti D antibody do

A

Attach to the Rh D antigens found on the foetal rbcs. This marks them to be destroyed.

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13
Q

What determines the nature of HBN to be mild, moderate or severe

A

The rate of haemolysis

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14
Q

What occurs in mild cases

A
  • The small increase in red cell haemolysis is tolerated by the foetus
15
Q

Symptoms (2) and tx of newborns with mild cases of HDN

A
  1. Mild anaemia
  2. Jaundice
    Both of these may resolve w/o tx
16
Q

What happens when there is an increased rate of haemolysis

A
  • Bilirubin may remain low during pregnancy as placenta can remove bilirubin from the foetal circulation
  • Post delivery the neonate’s immature liver is unable to metabolise the increased bilirubin accumulated in their blood
  • Within 24 hrs bilirubin may rise and enter the brain, causing kernicterus
17
Q

What is kernicterus and its prognosis

A

Kernicterus is a potentially fatal condition that leaves permanent neurological damage in the babies that survive.

17
Q

Complications of HDN (6)

A
  1. Anaemia -> in foetus & neonate
  2. Jaundice -> elevated bilirubin
  3. Kernicterus -> seen in jaundice infants where bilirubin crosses into the brain and attaches and damages the brain tissue
  4. Hydropic -> bloated w fluid
  5. Hydrops foetalis -> watery foetus suffering from oedema bloated w fluid
  6. Erythroblastosis foetalis -> large no.s of nucleated rbcs in foetal peripheral blood
17
Q

Testing of the mother (4 methods)

A
  1. Previous history -> of transfusions, pregnancies, infants affected by HDN
  2. ABO and Rh testing -> all Rh D- mothers must be identified
  3. Antibody screen -> should be performed using the IAT to detect IgG antibodies in the mother
  4. Antibody identification -> if antibody screen is positive, need to determine the identity of the antibody and its clinical significance
18
Q

How many times must antenatal mothers be blood grouped

A

At least twice

19
Q

What is performed to determine if a Rh+ mother has been sensitised to the Rh D antigen

A

An antibody screen is performed on her plasma

20
Q

What is given to unsensitised mothers to reduce the risk of future sensitisation

A

Anti-D Ig

21
Q

What does Anti D Ig do

A

Mops up any foetal rbcs that may have leaked into the mother’s circulation

22
Q

When do Rh- mothers receive anti D Ig (2)

A
  1. At about 28 wks gestation, which is about when the foetal rbcs start expressing the D antigen
  2. A few wks before labour begins (Risk of feto-maternal hemorrhage is high)
23
Q

When is the final dose of anti D Ig given

A

After the baby has been delivered if the baby is Rh +

24
Q

How is the father tested

A

By doing a Rhesus genotype, which predicts the chances of having a Rh + baby

25
Q

What are the chances of a Rh+ baby with a father who is homozygous DD

A

100% chance of foetus being Rh+

26
Q

What are the chances of a Rh+ baby with a father who is heterozygous Dd

A

50% chance of foetus being Rh+

27
Q

How can the level of haemolysis in the foetus be measured

A

The level of bilirubin in the amnion can be measured and is indicative of the level of haemolysis in the foetus

28
Q

What other ways is the foetus tested (4)

A
  1. Foetal blood sampling for blood group
  2. Direct Coombs test
  3. Hb (anaemia)
  4. Bilirubin (jaundice)
29
Q

What is the Doppler ultrasound used to test for in the foetus

A

Non invasive technique for measuring oedema and anaemia in the foetus

30
Q

How is the neonate (newborn) tested

A
  1. Cord blood taken (representative of neonatal sample)
  2. ABO and Rh of infant
  3. Direct Coombs test -> see if maternal antibody has attached to infant’s cells in utero
  4. Hb level to assess anaemia
  5. Bilirubin level to assess jaundice
31
Q

Management & tx of foetus with suspected HDN

A
  1. Intrauterine blood transfusions
  2. Early delivery solution to Hydropic baby -> prematurity has risks
    3.Phototherapy -> aids w excretion of bilirubin
  3. Top up blood transfusions post delivery
  4. Immediate exchange transfusion post delivery -> alleviate the hyperbilirubinaemia, correct anaemia

Transfusion Science (6 decks)

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