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Rhesus isoimmunisation: high risk pregnancy

The document discusses the mechanisms and management of Rh isoimmunization in pregnancies, detailing the incidence and diagnostic methods used for identifying Rh compatibility. It covers prophylaxis strategies for both antenatal and postnatal care, including administration protocols for anti-D immunoglobulin and screening for Rh alloimmunization. Additionally, it outlines the assessment and management of affected pregnancies, emphasizing the importance of monitoring fetal conditions and potential complications.

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Rh ISOIMMUNISATION
COMPETENCIES OF THE TOPIC  Mechanism of isoimmunisation in pregnancies  Prophylaxis  Fetal complications  Diagnosis  Management
INTRODUCTION  Landsteiner and Weiner in the year 1940, discovered Rh antigen. The individual having the antigen is called Rh-positive and in whom it is not present, is called Rh negative.  INCIDENCE- India- 5-10% Europe and American whites- 15-17% China -1 % Japan- almost nil
PATHOPHYSIOLOGY  ALLOIMMUNISATION- production of immune antibodies in an individual in response to foreign red cell antigen derived from another individual of the same species provided the first one lacks the antigen.  Incidence – 6 per 1000  METHODS OF ALLOIMMUNISATION- 1) As a result of pregnancy 2) Transfusion of mismatched blood Factors influencing alloimmunization- - Size of inoculum - Coexistence of ABO incompatibility between mother and fetus Types of antibodies- 1) IgM 2) IgG
GENETICS  Rh factor – 49 antigens.  Antigens located on 2 rhesus proteins- RhD and RhCE.  Both genes located on short arm of chromosome 1.  RhD gene- only RhD antigen  RhCE gene- four antigens ( E, e, C, c).  Rh positive- may be homozygous or heterozygous  Other blood group systems- K(Kell), Fya (Duffy), Jka (Kidd), Lewis group
DIAGNOSIS - Rh typing - Indirect coombs test - Antibody titre - Gel microcolumn assay Serious fetal anaemia is unlikely when serum levels of anti-D are <15 mIU /ml.
MANAGEMENT OF RH NEGATIVE NONIMMUNISED WOMEN DETECTION OF RH ALLOIMMUNIZATION - ABO and Rh typing at first visit - Screening for atypical antibodies- ICT - Repeated at 28 weeks - Paternal Rhesus typing - 4 weekly antibody screening in non-immunized pregnancy not universally accepted.
PREVENTION – ANTENATAL AND POSTNATAL PROPHYLAXIS Antenatal prophylaxis- - 1 dose regimen- at 28 weeks (300 microgram of anti-D) - 2 dose regimen- at 28 and 34 weeks (100 and 300 microgram of anti-D) - After anti D, titre should not be >4 at term  National Institute for Health and Care Excellence in England recommends fetal RhD genotyping.  In several countries like Denmark, Sweden, the Netherlands, England, France, Finland- fetal RhD genotype determination based on maternal cfDNA is being routinely done.
 POST-NATAL PROPHYLAXIS - Routine post-natal anti-D (300 microgm) – as soon as possible, preferably within 72 hours, can be given upto 10 days and even weeks. - Kleihauer Betke test (UK) done within 2 hrs of delivery to detect large feto- maternal haemorrhage to calculate dose of anti-D. Better test is flow cytometry. - 300 microgm= 1500 IU og anti-D= neutralise 15 ml of Rh positive fetal RBCs= 30 ml of fetal blood.
MANAGEMENT OF RH NEGATIVE IMMUNISED WOMEN - Paternal Rh phenotype and genotype- homozygous(100% affected) - Fetal blood group (if father is heterozygous)- CVS, amniocentesis, fetal blood sampling, maternal cfDNA(98.7 -100% ) - FIRST AFFECTED PREGNANCY- - maternal antibody titre most useful in first affected pregnancy. - Titre rarely exceeds critical level. - Serial quantification of antibody titres every 4 weeks until 28 weeks and then every 2 weeks. - SUBSEQUENT PREGNANCIES AFTER 1ST AFFECTED- - Predictor of severity- titre at which the at which the previous pregnancy was affected. Assessment of fetal anaemia 10 weeks prior to the gestational age at which previous pregnancy was affected.
ULTRASOUND ASSESSMENT- gestational age, fetal hydrops, cardiomegaly, increased umbilical vein diameter, hepato-splenomegaly, bowel wall. Also for invasive procedures. MCA PEAK SYSTOLIC VELOCITY- - superceded the invasive method of amniocentesis then spectrophotometric analysis for estimation of bilirubin. - Interval- 1-2 weeks - From 18 weeks to 36 weeks - PSV>1.5 MoM - cordocentesis
FETAL BLOOD SAMPLING AND INTRAUTERINE TRANSFUSION- - Placental end of umbilical cord - Needle in umbilical vein- ABO and Rh, Hb, haematocrit - Haematocrit 30%= 8 gm/dl of Hb= indication for intrauterine transfusion( intravenous or intraperitoneal) - Cordocentesis- 5% fetal death if performed before 24 weeks - Overtransfusion done so that interval between transfusion is 2-4 weeks. - Generally 3-4 transfusions required but 10 may be required in some. - IUT done upto 34 weeks. - After invasive procedure no use of antibody titre.
CARE AT DELIVERY- - Fetal surveillance reassuring- labour induced at 37-38 weeks. - Corticosteroids given if preterm delivery anticipated. - If delivery before 34 weeks then LSCS. DURING DELIVERY- - Keep cross-matched blood ready before induction of labour. - Clamp the cord immediately - Keep cord long for possible catheterisation - Collect cord blood- ABO and Rh typing, bilirubin, Hb, direct coombs test
Haemolytic disease of the fetus and newborn  Neonates from severely affected pregnancies are less likely to show signs of haemolytic disease HYDROPS FETALIS -most severe form -Severe anaemia, tissue anoxemia, metabolic acidosis - Hyperplasia of placental tissue - Hypoproteinemia(liver damage) - Congestive heart failure - Hydrops - Fetal death - Sonography – Buddha position
ICTERUS GRAVIDARUM NEONATORUM- - Baby born alive without jaundice but develops within 24 hours of birth. - If bilirubin>20 mg/dl- kernicterus CONGENITAL ANAEMIA OF NEWBORN - Mildest form of the disease. - RBCs destruction continues upto 6 weeks after which the antibodies are not available for haemolysis.
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