Determination of RH incompatibility

BLOOD TYPES
BLOOD TYPES
A, B, O blood groups are specific types of proteins found on the surface of RBC’s
Also found in the cells and other body fluids (saliva, semen, etc)
O represents neither protein being present on RBC
Possible groups include: A, B, AB, or O
A, B, O groups most important for transfusions

RH FACTOR
Proteins (antigens) occurring only on surface of RBC’s
Rh + if proteins present
Rh – if proteins absent
A+, A-, B+, B-, AB+, AB-, O+, O-
Most important for pregnancy
Inheritance is Autosomal Dominant
15% Caucasian population is Rh-

General Screening
ABO & Rh Ab @ 1st prenatal visit
@ 28 weeks
Postpartum
Antepartum bleeding and before giving any immune globulin
Neonatal bloods ABO, Rh, DAT

Gold Standard Test
Indirect Coombs:
-mix Rh(D)+ cells with maternal serum
-anti-Rh(D) Ab will adhere
-RBC’s then washed & suspended in Coombs serum (antihuman globulin)
-RBC’s coated with Ab will be agglutinated
Direct Coombs:
-mix infant’s RBC’s with Coombs serum
-maternal Ab present if cells agglutinate

+ Rh(D) Antibody Screen
Serial antibody titres q2-4 weeks
If titre ≥1:16 - amniocentesis or MCA dopplers and more frequent titres (q1-2 wk)
Critical titre – sig risk hydrops
** amnio can be devastating in this setting
U/S for dating and monitoring
Correct dates needed for determining appropriate bili levels (delta OD450)