HDFN

What causes HDFN?

Mother making IgG antibodies that cross the placenta and bind to fetal cells causing hemplysis

What groups cause severe HDFN?

Rh, Kell, Fya, Duffy

What groups cause mild HDFN?

ABO, Fyb

Which groups commonly cause HDFN?

ABO, Rh, Kell

What would the DAT results be for mother and newborn if HDFN has occured?

Mother is negative but newborn will be positive

What is RhIg?

Pooled human source of anti-D to be given to Rh neg mothers

What is the mechanism of RhIg?

Acts as a passive antibody incase fetal blood enters mother’s circulation during pregnancy and prevents her from developing an anti-D

What is the criteria for RhIg?

Mother has to be Rh neg and no active anti-D

When is RhIg given?

At 28 weeks and within 72 hours of delivery if baby is Rh pos or weak D pos

What is the standard dose and how much does it clear?

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

Can RhIg interfere with pretransfusion testing?

Yes because we may detect the passive anti-D up to 8 weeks later

What happens during prenatal testing?

Mother gets a type and screen to determine her blood group and if she has any active antibodies

What is the follow up mother screen is positive?

Full panel, titration, and Ag type mother and father

What titre level is significant for IgG antibodies?

16 or greater

Which antibody is significant for any titre level?

Anti-K because it is expressed early

What is a signficant rise in titre?

If it is 2 tubes or greater (8 to 32 is significant)

Is RhIg given is mother is already making an anti-D?

No because it is active

Is RhIg given is mother is Rh neg and the baby is Rh neg?

No because it will not sensitize her

What is the followup if baby has DAT positive cells?

Must do an elution to ID antibody and dissociation to antigen type baby