Anti-D

Question 1

What is the d antigen?

Answer 1

The D antigen is the most important antigen (on surfaces of RBC) of the rhesus system. With = RhD positive, without = RhD negative.

The process of sensitisation has no adverse health effects for the mother and usually does not affect the pregnancy during which it occurs.

Question 2

What is feto-maternal haemorrhage (FMH)?

Answer 2

small amounts of fetal blood can enter the maternal circulation

Question 3

What can happen due to a FMH? And what is the process called?

Answer 3

The presence of fetal RhD-positive cells in her circulation can cause a mother who is RhD negative to mount an immune response, produces antibodies against the RhD antigen. This process is called sensitisation or alloimmunisation

Question 4

When is sensitisation most common? What events can cause it?

Answer 4

Third trimester and during childbirth
chorionic villus sampling, amniocentesis or external cephalic version), terminations, late miscarriages, antepartum haemorrhage and abdominal trauma

Question 5

The risk of sensitisation depends on what? And when is it greatest?

Answer 5

The volume of fetal blood entering the mother’s circulation and the magnitude of the mother’s immune response. The risk of sensitisation is greatest in the first pregnancy and decreases with each subsequent pregnancy. Once sensitisation has occurred it is irreversible

Question 6

What can happen to the fetus if the mother is exposed to RhD antigen during a subsequent pregnancy after sensitisation in the previous one?

Answer 6

The immune response is quicker and much greater. The anti-D antibodies produced by the mother can cross the placenta and bind to RhD antigen on the surface of fetal red blood cells. These antibody-coated fetal red blood cells are removed/destroyed from the fetal circulation. Fetal anaemia results if the red blood cells are removed/destroyed faster than they are produced

Question 7

What is an antigen?

Answer 7

a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies

Question 8

What are effects of severe anemia on a fetus?

Answer 8

fetal heart failure, fluid retention and swelling (hydrops), and intrauterine death

Question 9

How can anaemia be treated before birth?

Answer 9

anaemia and hydrops can be managed with intrauterine transfusions, but this carries a 2% risk of fetal loss

Question 10

How is bilirubin cleared in utero?

Answer 10

When red blood cells are broken down, bilirubin is released. In utero this is cleared by the placenta and is not harmful.

Question 11

What is kernicterus (aka bilirubin encephalopathy )? What can it lead to?

Answer 11

Permanent brain damage that can be caused by developing jaundice left untreated. This can lead to a range of neurodevelopmental problems, such as cerebral palsy, deafness, and motor and speech delay

If levels very high, the bilirubin can cross the thin layer of tissue that separates the brain and blood (the blood-brain barrier)- can damage the brain and spinal cord

Question 12

What are the initial and progressive symptoms of kernicterus?

Answer 12

decreased awareness of the world around them –e.g. no reaction to clapping
unusually floppy muscles
poor feeding
As kernicterus progresses- seizures (fits) and arching of the neck or spine

Question 13

What is haemolytic anaemia?

Answer 13

Anaemia (reduction of RBCs or Hb) caused by hemolyiss (abnormal destruction of RBCs)
Causes high levels of bilirubin- can lead to jaundice

Question 14

What is the definition of haemolytic disease of the newborn?

Answer 14

In haemolytic disease of the newborn the maternal immune system has been ‘immunized’ against aspects of the baby’s blood group
Rhesus immunisation
ABO incompatability

Question 15

Why does haemolytic disease of the newborn occur?

Answer 15

Previous pregnancy or miscarriage where fetal blood enters maternal bloodstream
CVS or amniocentesis
RTA
ECV
Intrauterine death
Usually in the 3rd trimester or at delivery

Question 16

How can this be prevented?

Answer 16

Administration of Anti-D
After an event that may lead to feto-maternal haemorrhage e.g. after delivery, miscarriage, abortion, invasive procedures or abdominal trauma.
The anti-D immunoglobulin administered neutralises the Rh D fetal antigen
In addition, anti-D immunoglobulin can be administered routinely in the third trimester as prophylaxis against small amounts of FMH that can occur in the absence of observable sensitising event

Question 17

Routine administration of Anti D

Answer 17

NICE (2008) recommends:
2 doses (500iu) at 28 and 34 weeks        OR
2 doses (1000-1650iu) at 28 and 34 weeks   OR
1 dose (1500IU) at 28-30 week

Question 18

What is the care plan for after delivery?

Answer 18

Need to take blood samples:
Maternal blood (Kleihauer test) :
to determine the number of fetal cells in the blood
Fetal blood (usually cord blood) :
to determine fetal blood group
(Coombs test) to determine maternal antibodies

Question 19

4 facts about Anti D administration?

Answer 19

Blood product
A midwifery exemption
IM injection into deltoid muscle
Need informed consent

Question 20

What is the plan of care for delivery and postnatally if there is known rhesus isoimmunisation?

Answer 20

Immediate cord clamping
Immediate blood tests and transfer to SCBU
Immediate phototherapy or exchange transfusion depending on SBR level
Frequent monitoring of SBR
40% of affected babies need no treatment
95% survive with modern treatment

Question 21

What is ABO incompatibility? And what are possible effects?

Answer 21

Same principle as rhesus isoimmunisation but less severe consequences
For example, a mother of blood group O may develop A or B antigens (this is the most common)
Mother blood group A may develop B antigens
Mother blood group B may develop A antigens
(these are extremely rare)

Usually apparent before 36 hours old
May become anaemic and require blood transfusion
May become jaundice