Hemolytic Disease of the Fetus and Newborn

How does HDFN happen?

Maternal IgG antibodies cross the placenta and attach to fetal cells causing hemolysis

What can happen to the fetus in utero if HDFN occurs?

Anemia because rbc get destroyed or Erythroblastosis fetalis

What is Erythroblastosis fetalis?

When fetus makes more rbc to compensate leading to high retic count, nRBCs, polychromasia, macrocytes

What can cause HDFN?

Previous transfusion, pregnancy

How does HDFN usually affect the baby?

In the first pregnancy, the baby is usually unaffected but subsequent pregnancies, the baby will develop severe HDFN

What is seen in severe cases of HDFN?

Anemia, hyperbilirubinemia, hemoylisi

What are blood groups that cause severe HDFN?

Rh D, C, E, e, Kell, Fya, Kidd

What are blood groups that cause mild HDFN?

ABO, Fyb

What are blood groups not associated with HDFN?

Lewis, P, I

What is Rh Immune Globulin (RhIg)?

Human source of pooled plasma contain anti-D

How is RhIg manufactured?

Uses anion-exchange chromatography and solvent detergent + ultrafiltration to destroy virus, then lyophilized (free dried)

What is the mechanism of RhIg?

Not fully understand but though to mask epitope of D antigen

What is RhIg used for?

Given to Rh neg mothers to prevent ACTIVE anti-D production during pregnancy

Is RhIg active or passive immunity?

Passive since we are giving it to her, not the mother making it

Who is eligible for RhIg?

Rh neg females without an active anti-D (ab screen)

Why is RhIg given at 28 weeks?

Prenatal dose at 28 weeks to remove an Rh pos fetal cells in circulation before delivery

Why is RhIg given within 72 hrs of post-delivery?

Removes fetal cells that have entered mother’s circulationWh

When are additional doses of RhIg given?

Amniocentesis, trauma, incomplete abortion in case a bleed has happened

What is the standard dose of RhIg?

300ug that will clear 30mL of whole blood and 15 mL of packed cells

What are some disadvantages of RhIg?

Half life is 23-26 days so it may detected up to 8 weeks after, there are rare risks associated, it is not effective if mom is already making anti-D, and it does not prevent ab production to other blood groups

What are other cases where RhIg can be given?

Rh incompatible transfusions or treatment for Idiopathic Thrombocytopenic Purpura

Why is RhIg given in Rh incompatible transfusion?

It can help coat Rh pos antigens if Rh pos blood was given to Rh neg females < 45 years

Why is RhIg given to ITP?

Anti-D will bind to rbcs along with the autoantibody on the platelets. Spleen prefers to removed rbc over platelets so plts can stay in circulation

What is the prenatal testing follow up if the Ab screen is positive?

ID ab with panel, perform titration, Ag type mother and father

Does the Ab titre in the mother correspind to infant severity?

It may not correlateW

What is a significant titre for IgG anitbodies?

Titre of 16 or greater

What is a significant titre for anti-K?

Any titre is significantWh

What is considered a significant rise in titre?

Greater than two tubes. For example, 8 to 32 is significant bu 8 to 16 is not

If prenatal testing shows mom as A neg and Ab screen neg, is she given RhIg?

Yes because she is A neg

If baby is O neg, Weak D neg, DAT neg with A neg and Ab screen neg mom, is mom given RhIg?

No because baby is O neg so they are Rh compatible

If prenatal testing shows mom as A neg, Ab screen pos with Anti-D identified, is she given RhIg?

No because mom is already making an active anti-D

What is the follow up if baby is O pos and DAT pos when mom is A neg with active anti-D?

No post-natal RhIg is given to mother and an acid elution is done on DAT positive cells

If baby shows A 4+, B 1+, D4+ and DAT 1+ with O neg and Ab screen neg mother, what is the causes?

Wharton’s Jelly causing cells to stick together and giving weak pos reactions

What is the fetal bleed screen (Rosette Test)?

Performed on maternal sample 1hr after delivery to determine if more than 30mL of Rh pos fetal cells have entered the circulation

How does the Rosette test work?

Anti-D is added to mother’s samples to allow it to bind to Rh pos baby cells. It is then washed 4-6 times to get rid of mother cells. Indicator cells will be added and binds to the Anti-D on baby cells to cause agglutinationWh

What does a positive Rosette test mean?

Agglutination that is seen microscopically means more than 30mL of baby cells have entered circulation so mother is eligible for more RhIh

What is the Kleihaur-Betke test?

Test done on mother sample to quantify how many baby cells have entered circulation

How is the Kleihaur-Betke test done?

PBS is made from mom sample then treated with acid. Fetal cells will remain intact while mother cells are eluted out. Slides are washed then stained. Fetal cells will be counted per number of maternal cells then math

What is an intrauterine transfusion?

Transfusion when fetus is in utero

What blood is required for IUT?

Group O neg, less than 5 days old, CMV negative, irradiated, Ag neg and xm with maternal plasma

What is an exchange transfusion?

To remove some of baby blood to reduced Brb level, remove sensitixed calls and unbound maternal plasma then replace with donor whole blood

What blood is required for exchange transfusion?

Whole blood that is group O Rh specific, less than 5 days old, Ag neg and xm with maternal plasma