Haemolytic Disease of the Newborn may occur if the mother produces antibodies that cross the placenta and attack the foetuses red blood cells.
It can lead to anaemia in the baby, and in severe cases the foetus may die in utero, or suffer neurological damage after birth due to high levels of bilirubin (kernicterus).
Mother and foetus.
Haemolytic Disease of the Newborn may occur if we have a Rh (D) negative mother [RED dots] with an Rh (D) positive foetus [GREEN dots].
The Rh factor is the name given to a blood group protein, Rh (D), which is attached to red blood cells. Some people have this protein on their red blood cells and others do not.
On average, of every 100 people:
- 85 will have the Rh factor; their blood type is called ‘Rh (D) positive’
- 15 will not have the Rh factor; their blood type is called ‘Rh (D) negative’
During (or at the end of) her pregnancy, Rh (D) blood cells from the foetus enter the mothers blood stream (known as a sensitising event). Reasons for this occurring include:
- tests such as amniocentesis
- ectopic pregnancy
- termination of pregnancy
- abdominal trauma.
- following delivery of Rh(D) positive baby1.
Mum produces antibodies:
This stimulates the mother to produce antibodies (the pink lines in the diagram) to destroy the Rh (D) positive blood cells in the maternal blood. This RH (D) antibody response may remain for many years.
Antibody response to subsequent pregnancy:
The NEXT time the mother falls pregnant with an Rh (D) positive foetus, these antibodies may cross the placenta and attack the foetal red blood cells.
This can lead to Haemolytic Disease of the Newborn (HDN).
Prevention of HDN with Rh (D) immunoglobulin. Anti D.
As before, Rh (D) positive blood cells from the foetus may cross into the mothers bloodstream.
Rh (D) immunoglobulin given:
Within 72 hours, a dose of Rh(D) immunoglobulin is administered.
Rh (D) immunoglobulin is obtained form the fractionated plasma of blood donors.
Once administered, the Rh (D) immunoglobulin removes the Rh (D) positive red blood cells from the maternal bloodstream.
With these red blood cells removed, the mothers immune system is not activated and no maternal antibodies are produced.
Blood should be drawn from the mother prior to giving the immunoglobulin to assess the level of foetalmaternal hemorrhage. If the hemorrhage is larger than that covered by the initial dose of immunoglobulin additional dose(s) may be required.
No immune response:
Therefore at the next pregnancy there are no circulating antibodies to attack the foetal red blood cells.
In Australia Anti-D immunoglobulin is given to to all Rh negative women at 28 and 34 weeks gestation as prophylaxis against small amounts of foetal maternal bleeding that can occur in the absence of observable sensitising events. This is known as routine antenatal anti-D prophylaxis (RAADP).
Giving Rh(D) immunoglobulin (Anti-D):
The recommended dose of anti-D immunoglobulin is
- 250 IU after sensitising events in the first trimester of pregnancy and
- 625 IU after sensitising events beyond the first trimester.
Should be given ASAP and within 72 hrs of sensitising event.
If the gestational age is not known with certainty and the possibility exists that the gestational age is 13 weeks or more, 625 IU should be given.
- Should be administered at room temp.
- Give IMI slowly.
- If dose more than 5ml then divide and give at different sites.
- Rh(D) Positive mother.
- individuals with isolated Immunoglobulin A (IgA) deficiency, unless they have been tested and shown not to have circulating anti-IgA antibodies
- Mothers with severe thrombocytopenia or coagulation disorders that would contraindicate IM injections.
- NOT to be administered IVI (high risk of anaphylactic reaction).
- Monitor closely if mother has history of allergic reactions following human immunoglobulin preparations.
Anti-D manufactured from human plasma. Potential risk of virus (inluding Hep B, HIV, Creutzfeldt-Jakob Disease), but this if very low due to screening process for donors and viral inactivation processes during the manufacturing process.
- A small number (1.5 – 1.8%) of Rh negative mothers are immunised by their Rh positive foetuses despite administration of anti-D immunoglobulin postpartum. Studies have shown that this number can be reduced to less than 1.0% by administering two doses of anti-D immunoglobulin, the first at 28 weeks gestation and the second following delivery. [↩]