Antibodies in Pregnancy

Samples on patients who have developed significant red blood cell antibodies may be required more often than usual, the frequency of which will be indicated on the antenatal report. The samples are required to monitor the strength (titre) of the antibody(ies) concerned and to identify pregnancies which may be at risk from Haemolytic Disease of the Newborn (HDN). They also monitor the possible formation of additional allo-antibodies during the pregnancy. Patients who have developed red cell antibodies should be referred to an obstetrician.

The current guidelines state that women with anti-c, D, K or K related antibodies require a titre check every 4 weeks until the 28th week of pregnancy and thereafter every 2 weeks until delivery. Other specificities commonly implicated as causing HDN include anti-C, E, Fya & Jka though there are many rarer antibodies.

Anti-Lea, Leb, N, Lua, P1, H and A1 are not considered to be clinically significant as regards HDN.

In some instances, a paternal sample may be requested. This is usually to determine the fathers phenotype and predict the likelihood of the foetus carrying the relevant red cell antigen, thus indicating whether the possibility of HDN exists.

The red blood cell membrane contains numerous antigenic molecules which may induce the production of plasma antibodies. Currently there are more than 600 known red cell antigens. Immunisation is caused by exposure to 'foreign' red cells via pregnancy or transfusion though some plasma antibodies are naturally occurring.

The following table shows important antibodies that are usually encountered :

Blood Group System
 
Antibody
 
Causes Transfusion
Reaction?
Causes HDN?
 
% Blood
 Compatible
Rhesus
Anti-c
Probable
Common
20
Rhesus
Anti-C
Probable
Possible
32
Rhesus
Anti-Cw
Probable
Possible
98
Rhesus
Anti-D
Probable
Common
15
Rhesus
Anti-e
Probable
Possible
2
Rhesus
Anti-E
Probable
Possible
71
Kell
Anti-k (Cellano)
Probable
Possible
0.2
Kell
Anti-K
Probable
Possible
91
Kell
Anti-Kpa
Probable
Possible
98
Duffy
Anti-Fya
Probable
Possible
 34
Duffy
Anti-Fyb
Probable
 Possible 
 17
Kidd
Anti-Jka
Probable 
Possible
 23
Kidd
Anti-Jkb
Probable 
Possible
 26
Lewis
Anti-Lea
 Rare 
 Unlikely 
 78
Lewis
Anti-Leb
Unlikely
Unlikely
 28
MNS
Anti-M
Unlikely
Unlikely
 22
MNS
Anti-N
 Unlikely 
 Unlikely 
 28
MNS
Anti-s
Probable 
 Possible
 11
MNS
Anti-S
Probable 
 Possible
 45
MNS
Anti-U
Probable 
 Possible
 <0.1
P
Anti-P1
Unlikely 
Unlikely
 21
 Lutheran
Anti-Lua
Unlikely 
 Unlikely 
 92
 Lutheran
Anti-Lub
Probable 
Possible
 <0.2

Back to Antenatal Testing.


Page updated: 16/12/2010 | Updated by: Reg Rabett

Antibodies in Pregnancy