Chapter 12 Hemolytic Disease of the Fetus & Newborn Flashcards
What is HDFN also known as?
Erythroblastosis fetalis.
What occurs immunologically in a fetomaternal hemorrhage?
Maternal antibodies can form due to fetal cells getting into the maternal circulation.
What can cause a fetomaternal hemorrhage?
- Delivery (when placenta separates).
- Amniocentesis.
- Abortion (spontaneous or induced)
- Cordocentesis
- Ectopic pregnancy
- Abdominal trauma
Note: For most women a small amount of fetal blood enters the maternal circulation during the birthing process. Usually less than 30 mL. More than 30mL occurs 0.4% of the time.
What happens in the baby as red cells are destroyed due to HDFN?
Bilirubin (indirect) levels increase.
Remember:
Indirect Bilirubin = Unconjugated
What are the cause of most maternal IgG’s that result in HDFN?
Previous pregnancies.
Only 4% are due to formation of antibodies from transfusion exposure to foreign RBC antigens.
What does the fetus lack to convert unconjugated to conjugated bilirubin?
Enzyme glucoronyl transferase.
What is the process as heme is broken down?
- Heme is broken down –> converts to unconjugated bilirubin. Not soluble in water and attaches to albumin and goes to the liver.
- Enzyme glucoronyl transferase adds a carbohydrate to it to make it conjugated bilirubin.
- Goes to bile, then to intestines. Broken down by bacteria and is eliminated in the stool. Also is water soluble and can be excreted in urine as well.
How is indirect bilirubin processed for the fetus?
Indirect bilirubin crosses through the placenta and is conjugated by the maternal liver.
In HDFN, what is the result of fetal erythropoiesis?
As RBC destruction continues:
1. Erythroblasts are released (erythroblastosis fetalis), spleen and liver may enlarge.
2. Edema occurs in the peritoneal and pleural cavities (hydrops fetalis).
What can be the result in the fetus if it has uncompensated anemia?
Cardiac failure may result.
What is the difference right after birth on how the baby processes bilirubin?
- No new Abs entering the neonate.
- Newborn cannot conjugate bilirubin as it lacks glucuronyl transferase.
- Unconjugated bilirubin binds to albumin and then to tissues (jaundice).
- Permanent brain damage (kernicterus) may result if bilirubin binds to tissues of the central nervous system - this can be fatal.
Look at the diagrams on Slide 9 (p288 of TB).
What are normal bilirubin levels after the baby is born?
<1 day - 24 to 149 umol/L
1 to 2 days old - 58 to 197 umol/L
3 to 5 days old - 26 to 205 umol/L
Then in normal situations, the infant starts to produce the enzyme and levels of unconjugated bilirubin drop right off.
5 days to 60 years old - 5 to 21 umol/L.
What are the three important factors that must occur for HDFN to occur?
- RBC Ab must by IgG
- Fetus must possess an antigen that the mother lacks. (Gene is inherited from the father).
- Ag must be well developed at birth.
- Lewis, Lutheran, I, IH, P1 NOT well developed.
- Can be Rh (D), ABO or other antibodies.
What antigen group causes the most severe HDFN?
Rh group most severe.
D-neg women are sensitized during the 1st pregnancy with a D-pos baby (w/o intervention).
–> Subsequent pregnancies are affected.
In Rh HDFN if the baby’s blood has the DAT test what is the result?
Positive direct antiglobulin test (DAT).
If the baby has HDFN what are the symptoms?
Jaundice and/or anemia may occur.
What extreme treatment may be required for the baby with HDFN?
Exchange transfusion may be necessary.
What is the preventative treatment for Rh HDFN?
Rh immune globulin (RhIG) given to Rh neg expectant individuals to prevent Rh HDFN.
[Can be called RhoGam in other countries.]
Note: Before RhIG, D antibodies were responsible for 95% of all HDFN cases. Now it is almost no more common than other HDFN fatalities but still the most common.
What is the most common type of HDFN at 1 in 125 births?
ABO HDFN.
What is the blood group situation that causes ABO HDFN?
Mom: Group O
Baby: Group A or B blood.
Group O people have Anti-A,B that is IgG and can cross the placenta even in the first pregnancy. Most common but very mild.
Why are symptoms of ABO HDFN mild? What are the mild symptoms?
Possibly due to:
1. A or B substances in tissue that may neutralize Abs.
2. Fetal/infant RBCs may be poorly developed.
3. Fetal/infant RBC sites may be reduced.
Some jaundice may occur.
What is used to treat mild symptoms of ABO HDFN?
Phototherapy can be used to treat jaundice.
What other blood group types/antibodies can cause severe HDFN?
Other Rh, Kell, Kidd, Duffy (Fya), S, and U antigens have caused severe HDFN.
Any IgG can cause HDFN.
What blood groups/antibodies have caused mild cases of HDFN?
ABO, i, Fyb and Lutheran antibodies have caused mild HDFN.