Rh Factor ISOIMMUNIZATION Associate Professor Iolanda Blidaru MD

Rh Factor ISOIMMUNIZATION • Associate Professor Iolanda Blidaru, MD, Ph. D

INTRODUCTION R. B. C. Plasma ANTIGEN ANTIBODY >400 Agglutinogens on the cell membrane Natural & Immune Agglutinins/ Isoantibodies Antigen-Antobody reaction on the cell surface ® Hemolysis

INTRODUCTION Antigens • controlled by genes at chromosomal loci • appeared by 40 days of i. u. life • unchanged till death • present in tissues and tissue fluids Blood group system - a group of antigens controlled by a locus having a variable no. of allele genes.

INTRODUCTION Antigens • > 15 recognised blood group systems ABO, Rh, Kell, Duffy, MNS, P, Lewis, Lutheran, Xg, Li, Yt, Public antigens & Private antigens. • Blood-type means individual antigen phenotype which is the serological expression of the inherited genes. • Most of these blood group antigens have been found to be associated with hemolytic disease. • ABO & Rh account for 98%.

INTRODUCTION Antibodies Alloantibodies / Agglutinins Pre-existent Ig. M Iso-antibodies Ig. G Formed in response to foreign R. B. C. or soluble blood group substances

INTRODUCTION Pre-existent (natural) Antibodies • Formed against most of the major group antigens and present in individuals. • Ig. M type. • Do not cross placenta. • React poorly at body temperature (except anti-A and anti-B), but agglutinate erythrocytes at 5 -20°C

INTRODUCTION Iso-Antibodies • The isoantibodies are Ig. G. • Best react at body temperature • Cross the placenta readily. • Most Ab are complement binding.

Immunology of Rhesus Blood Group System • First demonstrated by testing human blood with rabit anti sera against RBC of Rhesus monkey → classifying into Rh negative / Rh positive. • The genotype is determined by the inheritance of 5 closely linked allelic genes situated on the short arm of chromosome 1, named as D, C, c, E, e (Fisher-Race). • No ”d” → absence of D • The foetus inherits one gene from each group as a haplotype such as sets of c. De, CDE, etc from each parent.

Immunology of Rhesus Blood Group System • 12 sets of combinations and 78 genotypes are possible. • For clinical and all practical purposes it is enough to know whether one is Rh POSITIVE or NEGATIVE against anti D sera. • The antigenic expressions of these genes are the coresponding antigens, consisting of C/c, D/d, E/e. • The antigenic determinants form an intrinsic part of the red cell membrane protein structure.

Immunology of Rhesus Blood Group System • C/c and E/e are weak antigens. • ‘D’ is the most immunogenic in the Rh system. • There is a rare type of Rh negative called Rh null who lack all known Rh antigens. • ‘D’ antigen has no natural antibody. • A single transfusion of Rh+ blood to a Rh– person has a 50% chance of forming anti Rh D antibodies.

Incidence of Rhesus Blood Group System Incidence of Rh negative varies in different races and ethnic groups • Mongoloids = nil • Chinese, Japanese = 1 -2% • Indians = 5% • Africans = 5 -8% • Causcasians = 15 -17% • Basques = 30 -35%

Pathogenesis Of Rh Iso-immunization Rh Negative Women Man Rh positive (Homo/Hetero) ß Rh Neg Fetus ¬ No problem ¬¬ ß Fetus ® ® Mother previously sensitized Secondary immune response ß Iso-antibody (Ig. G) ( ) ß Fetus ß Haemolysis ® Ü Ü Rh positive Fetus ß Rh+ RBCs enter maternal circulation ß Non sensitized mother Primary immune response ß Fetus ® unaffected 1 st baby usually escapes. Mother gets sensitised? ± Ü

Pathogenesis Of Rh Isoimmunization • Chances of feto-maternal hemorrhage / passage are only 5% in 1 st trimester but 47% in 3 rd trimester; many conditions can increase the risk. • Chances of primary sensitization during 1 st pregnancy is only 1 -2%, but 10 -15% of patients may become sensitized after delivery. • ABO incompatibility and Rh non-responder status may protect. • Amount of antibodies that enter the fetal circulation will determine the degree of haemolysis.

Pathology Of Erythroblastosis fetalis AFTER BIRTH Ü HAEMOLYSIS Þ ß ß Jaundice Kernicterus Hepatic Failure ß DEATH ANAEMIA ß INTRAUTERINE DEATH ERYTHROBLASTOSIS FETALIS ß IN UTERO ß BILLIRUBIN ß HEPATIC ERYTHROPOIESIS & DYSFUNCTION MAT. LIV → NO EFFECT ß Ü PORTAL & UMBILICAL VEIN HYPERTENSION, HEART FAILURE, HYDROPS FETALIS ß BIRTH OF AN AFFECTED INFANT - Wide spectrum of presentations. Rapid deterioration of the infant after birth. May continue for few days to few months. ß ß ß

Antenatal Diagnosis Of Rh Isoimmunization • the history and physical exam. • the maternal and paternal Rh blood type • anti-Rh Ab screen (monthly after 20 -th week) – by indirect Coombs test; if positive as 1/8 -1/32, there is needed further assessment • ultrasound exams • fetal anemia and hyperbilirubinemia – by ultrasound guided amniocentesis → spectrophotometry of amnionic fluid (Liley chart) → CORDOCENTESIS – fetal blood tests

Antenatal Diagnosis Of Rh Isoimmunization - ultrasound exams

Antenatal Diagnosis Of Rh Iso-immunization • Liley chart

Antenatal Diagnosis Of Rh Iso-immunization

Postnatal Diagnosis Of Rh Isoimmunization Hemolytic disease of the newborn • Hemolytic anemia (Hb = 13 -14 g%; bilirubin < 3. 5 mg%) • Icterus gravis neonatorum (Hb = 712 g%; bilirubin > 10 mg%) • Kernicterus (bilirubin > 18 mg%) • Hydrops fetalis (Hb < 7 -12 g%; bilirubin > 10 mg%)

Postnatal Diagnosis Of Rh Iso-immunization

Hydrops fetalis

Hydrops fetalis

Postnatal Diagnosis Of Rh Iso-immunization Laboratory tests (newborn) • ABO and Rh blood group test • Hb and Ht • Reticulocyte count • Bilirubin level • Direct Coombs test

Prevention of Rh Isoimmunization • Premarital counseling. • Blood grouping for every woman, before 1 st pregnancy. • Proper management of unsensitised Rh negative pregnancies.

Prevention of Rh Isoimmunization v Blood typing at 1 -st visit, If negative → husband’s typing. v Anti-Rh Ab screen (indirect Coomb’s test) of Rh–negative mother. v At about 28 weeks – negative → 300μg anti D immunoglobulin. v In abortion, ectopic pregnancy, abruption of placenta, placenta praevia, molar pregnancy, abdominal trauma, chorionic villi sampling, amniocentesis = foetal-maternal hemorrhage → 150 -300μg anti D v At birth- cord blood for ABO and Rh typing → Baby Rh positive → 300μg anti D within 72 hours of delivery

Prevention of Rh Isoimmunization In case of large fetal-maternal hemorrhage: 1. the Kleihauer-Betke test estimates the amount of fetal blood in circulation 2. the indirect Coombs test 3. an additional dose of anti-D, if needed

The Kleihauer-Betke test

Prevention of Rh Isoimmunization Errors - Causes of sensitization • Misinterpretation of maternal Rh type • Rh+ blood transfusion • Unprotected pregnancy and labour • Inadequate dose / improper use of Ig. G on previous occasions • Immunization to cross-reacting antigen

Management of Rh Isoimmunized Pregnancy ANTEPARTUM • Careful planning during antepartum, intrapartum and neonatal period • Known repeated maternal anti-D Ab titer • Intrauterine fetal monitoring with repeated US examinations, cordocentesis & fetal blood sampling / amniocentesis, the measurement of the fetal middle cerebral artery peak velocity (Doppler)

Management of Iso- immunized Pregnancy • Fetus Rh Positive + anemia • Intrauterine transfusion of Rhnegative blood in selected cases • Planned preterm delivery any time after 34 weeks or as soon as the lung maturity is documented by inducing the labor or cesarean section (for the severely affected fetuses)

Management of Iso- immunized Pregnancy POSTPARTUM Management of the infant • Monitoring up to 8 weeks • Exchange-transfusion in the newborn in the umbilical vein • Phototherapy • In cases of severely sensitized women, consider medical termination of pregnancy and sterilization.