Rh antigens and their role in alloimmunization during pregnancy. The document discusses Rh antigens, specifically the D antigen which is the most immunogenic. It covers the pathophysiology of Rh isoimmunization, causes of maternal alloimmunization, effects on the mother and fetus, management including prevention with Rh immune globulin administration, and treatment options. Laboratory tests helpful for diagnosis and monitoring are also outlined.

1. RH ANTIGENS AND IT’S ROLE
ALLOIMMUNIZATION IN
PREGNANCY
Presented by ALAWODE F.A
DEPARTMENT OF MEDICAL LABORATORY
SCIENCE
UNIOSUN Teaching hospital, Osogbo

2. OUTLINE
2
•Introduction
•Rh antigens
•incidence of Rh antigens
•Pathophysiology of Rh Isoimmunisation
•Causes of Maternal Isoimmunisation.
•The Risk of development of Maternal isoimmunisation
•Effects on mother.
•Effect on fetus
•Management
•Laboratory investigations.
•Treatment of Rh isoimmunisation.
•Conclusion
•Recommendation
•Selected references

3. INTRODUCTION
• Isoimmunization is the production of antibodies in
response to an antigen derived from another individual
of the same species
• Maternal Rh alloimmunization, also known as
isoimmunization, occurs when a woman’s immune
system is sensitized to foreign erythrocyte surface
antigens, stimulating the production of
immunoglobulin g (igG) antibodies
• (Aitken and Tichy., 2015)

4. Rh antigens
4
• At present, the Rh blood group system consists of 50
defined blood group antigens, among which the five
Antigens “D, C, c, E, e’’ are the most important.
• The D antigen is considered to be the most
immunogenic
• The D Antigen, also called the Rh factor is the most
immunogenic of them, though the others are still
clinically relevant.
(Salem and Singer, 2014)

5. INCIDENCE
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Nigerian studies showing the incidence of
Rh “D’’ negativity;
• 4.5% prevalence rate at Enugu, Southeast
(Okeke et al.,2012)
• 0.7% incidence rate at Kaduna, North
(Onwuhafua, 2014)
• 5.5% prevalence rate at Ogbomosho, Southwest
(Adeyemi AS and Bello-Ajao, 2016)

6. PATHOPHYSIOLOGY
6
Rh alloimmunization usually occurs when:
• the fetus has Rh-positive erythrocytes, and the mother
has Rh negative erythrocytes;
• the mother has the immunogenic capacity to produce
antibody directed against the fetal’s D antigen;
• a sufficient number of fetal erythrocytes gains access to
the maternal circulation.
(Aitken and Tichy., 2015)

7. CAUSES OF MATERNAL
ALLOIMMUNIZATION
• Blood transfusion
• Abortion
• Obstetric procedures
 Amniocentesis
 Chorionic villus sampling (CVS)
 Percutaneous umbilical blood sampling (PUBS)
 External cephalic version (ECV)
 Manual removal of the placenta
• Abdominal/pelvic trauma
• Fetomaternal hemorrhage
• Antepartum haemorrhage (placenta praevia, abruptio)
• Intrauterine foetal demise
• Ectopic pregnancy
• Caesarean delivery
(Fan et al., 2014)

8. PATHOPHYSIOLOGY
8
• Foeto-maternal haemorrhage may occur during pregnancy
(10%) or delivery (90%)
• Notwithstanding, foetal RBCs have been detected in the
maternal blood in all three (7, 16, 29) trimesters without an
apparent predisposing factor
• The amount of foetal blood necessary to produce Rh
incompatibility varies, but as little as 0.1 mL of Rh+ cells have
been documented.
• Studies have suggested that up to 30% of persons (non-
responders) with Rh- blood never develop Rh incompatibility
even when challenged with large volumes of Rh+ blood

9. Figure 1. Pathogenesis of Rh isoimmunisation
Source: www. medscape.com

10. EFFECTS ON FETUS
10
SEQUENCE OF INUTERO EVENTS:
Maternal IgG enters foetal circulation via placenta
Destruction of foetal red cells occur - foetal
anaemia
[HCT<30%]
Haem is formed and converted to bilirubin –
foetal hyperbilirubinaemia
Both are neurotoxic, but effectively cleared by
placenta and metabolised by the mother
Extramedullary erythropoeisis is stimulated
Immature erythroblasts are produced (Haaspel

11. Effects on neonates
11
When cell destruction exceeds production
Severe anaemia occurs
More demand on extramedullary sites to produce more
red cells
– hepatosplenomegaly
Heart failure eventually results, with ascites, oedema and
pericardial effusion – erythroblastosis foetalis
Hydrops foetalis, occurs when the haematocrit falls
below 15%. Often results in foetal death shortly before or
after birth (Haspel and westhoff., 2015)

12. THE RISK OF DEVELOPMENT OF
MATERNAL ISOIMMUNISATION IS
DETERMINED BY...
12
• the husband phenotype and genotype ( 40 % of Rh
positive men are homozygous and 60% are
heterozygous).
• The antigen load and frequency of exposure.
• difference in immunogenicity of antigen

13. Laboratory investigations
ANTENATAL
• Rh blood typing
• Antibody screening test
• Rh antibody titers
• Rossette screening test
POST NATAL
• Direct coombs test, ABO and Rh blood typing,full
blood count , hemoglobin levels and serum bilirubin
levels.
• Kleihauer-Betke test (Acid elution test) (Sandler et
al., 2012)

14. Figure 2. Direct coombs test
14
Source: www. medscape.com

15. Figure 3. Indirect Coombs Test
15
Source: www. medscape.com

16. Management
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The objective of antenatal management is
– Prevention of Rh alloimmunisation in the Rh-
negative unsensitised woman
Early detection and treatment of foetal anaemia in
the sensitised woman
(Moise and Argoti., 2012)
–

17. Management
This includes history taking, clinical examination,
appropriate investigations, and treatment
Two groups of women are catered for
02/09/16 17
–
–
Unsensitised Rh-negative women
Sensitised Rh-negative women
There is usually no specific finding on the history
and clinical examination for the woman that is not
sensitised

18. ... MANAGEMENT ...
18
Postpartum management
Involve the neonatologist
Send cord samples for ABO/Rh typing, DCT, Hb,
bilirubin levels, peripheral smear
If foetus is Rh-negative, no further intervention
If foetus is Rh-positive, The dose of Rh IgG to be
administered can be determined through Rosette
foetal RBC screening and Acid elution (Kleihauer-
Betke) test.

19. TREATMENT
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• Intrauterine Blood Transfusion-recommended
treatment for severe (haemolytic) anaemi inutero
• An urgent exchange blood transfusion is indicated in
moderate to severely affected neonates
• Phototherapy for mild affectation
(Saxena.,2010)

20. PREVENTION
• Administration of Rh immune globulin prophylaxis
at 28th week of gestation and within 72 hours after
delivery
• Women should receive a low dose whenever there is
any sensitizing events (bleeding, miscarriage,
threatened abortion ,ectopic pregnancy e.t.c)
(Moise and Argoti., 2012)

21. Recent Advances
21
• Point-of-care-tests (POCT), i.e., rapid tests for
determining Rh status
• A lower 50 mcg dose preparation of Rh IgG for
use following first trimester abortions
• Concept of partial D (usually test positive, but
can also form anti-Rh antibodies)
(Kemper et al.,2022)

22. Recommendations
22
• Advocacy for partnership by Government and
NGOs to help subsidize the cost of the
immunoglobulin
• Special insurance cover for Rh-negative women
to ensure ease of procurement when needed
• Involvement of clergy as part of premarital
counsellors
• Creation of special groups for Rh-negative people
where potential Rh-negative spouses can be met

23. Conclusion
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 Rhesus alloimmunisation is a real problem and real
efforts need to be made to mitigate its impact
 Although its incidence has decreased dramatically,
yet the consequences of haemolytic disease of the
newborn remain
 Great advancements have been made in the detection
and management of this condition.

24. THANK YOU
FOR
LISTENING
02/09/16 24

25. SELECTED REFERENCES
25
Aitken, S.L., Tichy, E.M. (2015). Rh (O)D immune globulin products for prevention of alloimmunization
during pregnancy. American Journal of Health System Pharmacy.72 (4): 267-76
Adeyemi, A.S., Bello-Ajao, H.T.(2016).Prevalence of Rhesus D-negative blood type and the challenges of
Rhesus D immunoprophylaxis among obstetric population in Ogbomosho, Southwestern Nigeria.
Annals of Tropical Medicine and Public Health.9(1):12-15.
Fan, J., Lee, B.K., Wikman, T., Johnson, S., Reilly, M. (2014). Associations of Rhesus and non-Rhesus
maternal red blood cell alloimmunization with still birth and preterm birth. International Journal of
Epidemiology. 43 (4):23-31
Haspel, R. L.,Westhoff, C. M . (2015).”How do I manage Rh typing in obstetric patients?;managing obstetric rh
typing’’.Transfusion. 55 (3): 470-474.
Kemper, A.R., Newman, T.B., Slaughter. J.L., et al. (2022). Clinical practice guideline revision:
management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics.
150 (3): e2022058859
Moise, K.J., Argoti, P.S. (2012). Management and prevention of red cell lloimmunition in pregnancy :
systemtic review . Obstetrics and Gynaecology .120-1132

26. Selected references
Okeke, T.C., Ocheni, S., Nwagha, U.I., Ibeghulam, O.G. (2012). The prevalence of Rhesus
negativity among pregnant women in Enugu, Southeast Nigeria. Nigerian Journal of
Clinical Practice. 15(4): 400-2
Onwuhafua, J.A. (2014). Pregnancy in Rhesus Negative Women in Kaduna, Northern
Nigeria. Tropical journal of Obstetrics and Gynaecology. 21(1): 21-23
Salem, L., Singer, K.R. Rh Incompatibility. [Updated: Feb 06, 2014]. Available from
http://emedicine.medscape.com/article/797150
Saxena, R., editor. Bedside Obstetrics and Gynaecology. 1st ed. New Delhi: Jaypee Brother
Medical Publishers (P) Ltd; 2010: 105-120.