Rh iso immunization

introduction and effects of RH isoimmunization.

1. Rh-ISOIMMUNIZATION IN PREGNANCY

2. Rh Isoimmunization

3. Introduction Isoimmunization : Production of antibodies in response to an antigen derived from another individual of the same species Rh isoimmunization : M aternal antibody production in response to fetal red blood cell Rh antigen,when mother Rh- ve ,fetus Rh+ve .

4. Introduction of ABO blood group system Four blood types(A, B, AB & O) Each blood type is additionally classified according to the presence or absence of Rh factor

5. Rh alleles : Cc , Dd and Ee . D antigen, the most potent, its presence or absence denotes an individual to be Rh + ve or – ve . DD-homozygous, Dd -heterozygous, dd - negative.

6. Pathophysiology 1st Rh+ve pregnancy:   Rh negative mother bearing Rh positive fetus Feto -maternal bleed:   Abortion(Spontaneous 3-4%, Induced 5%) Amniocentesis, CVS, Cordocentesis Antepartum hemorrhage Abdominal trauma Ectopic pregnancy External cephalic version Third stage of labor Cesarean section  

7. Incidence of Iso -immunization is only 2-16% because of following factors : ABO incompatibility : confers protection against RH antigen Critical sensitizing volume: 0.1 ml Inadequate placental transfer of immunoglobulins Rh-stimulus non-responders Difference in immunogenicity of antigen

8. EFFECTS ON FETUS There is no risk 1 st trimester abortion in RH isoimmunization unless a/w other congenital anomalies Effects of RH isoimmunization is not evident till second trimester of pregnancy only after 2 nd trimester the reticuloendothelial system of fetus is developed and RH antigens are formed in utero

9. 1.CONGENITAL ANEMIA OF NEWBORN: mildest form( Hb : 12 g/dl) About 50% extramedullary hematopoiesis leading to liver and spleen enlargement 2.ICTERUS GRAVIS NEONATORUM: moderate(Hb:7-12 g/dl) about 25-30% unconjugated hyperbilirubinemia critical level of 20mg/100ml bilirubin: kernicterus Features: loss of moros reflex, posturing, poor feeding bulging anterior fontanelle high pitched cry,seizures

10. HYDROPS FETALIS

11. Effects on mother Rh isoimmunization is suspected in utero when mother develops: 1.Polyhydraminos 2.Pre eclampsia 3.Maternal syndrome: generalized edema, proteinuria , pruritus due to cholestasis Other complications: 4.Post partum hemorrhage: big plaenta and blood coagulopathy 5.DIC: retention of dead fetus in utero

12. Management of Rh isoimmunisation Prenatal Diagnosis Maternal: History: Previous episodes of possible sensitization (Causes of feto -maternal bleed and prior Rh+ baby ) ABO and Rh Blood groups of mother and father  

13. Antibody screening : Indirect Coomb’s test If + ve : test serially for high titers of maternal anti-Rh IgG (Critical level: >1:16) If antibody titre + ve , then repeat monthly- sudden rise is significant If – ve at 12 th  week : 1.Primigravida : Repeat at 28 th  and 36 th  week 2.Multigravida : Repeat at monthly intervals from 24 th  week onwards

14. 2.Fetal Serial Amniocentesis : for estimation of bilirubin in amniotic fluid A . Indications of amniocentesis i .High antibody titre (>1:8) ii.Previous severely affected baby B . Time i . No history of previously affected baby :30-32 weeks then repeat after 3-4weeks ii. Previously affected baby: >10 weeks prior C. Analysis :  Spectrophotometry of bilirubin contained amniotic fluid is done and plotting is done and optical density of the fluid at wavelength 450 nm is plotted in Liley’s chart. The deviation bulge obtained is directly proprtion to the severi ty

15. Ultrasonography Polyhydraminos Fetal hepatosplenomegaly , Bowel wall edema ( Extramedullary hematopoiesis ) Cardiomegaly , pericardial effusion Scalp and limb edema Abnormal fetal posture (Buddha position ) Sluggish fetal movement Placental hypertrophy and thickening

16. Middle Cerebral Artery Peak Systolic velocity (most accurate)

17. Cordocentesis (PUBS)

18. Treatment Unimmunised mother : expectant till term, but not to exceed the expected date of delivery Immunised mother : terminate pregnancy after maturity if evidence of hemolysis, previous history of still birth, sudden rise in antibody titre , or guided by optical density 450 in Liley’s chart or MCA systolic velocity or fetal Hematocrit

19. Zone I : continue till term, baby unlikely to be affected Zone I I:  may require premature termination beyond 34 wks Zone III :  severely affected baby. Imminent fetal death. Termination if >34 wks. If <34wks intrauterine transfusion repeatedly till 34 wks then terminate .

20. Cordocentesis MCA Peak Systolic velocity IUT

21. Care during delivery Vaginal delivery : Careful fetal monitoring, Gentle handling of uterus in 3 rd  stage of labor No prophylactic ergometrine Cesarean Section : Avoid blood spillage into peritoneal cavity and Manual removal of placenta Clamping umbilical cord : Quickly done and cord kept long (15-20cm) for exchange transfusion if needed Collection of cord blood for investigations : ABO and Rh blood group, Hb , Bilirubin, Direct Coomb’s test

22. Intrauterine transfusion : for severely affected fetus before 34 wks. Can be started at 18 wks , repeat at 1-3 wks interval upto 30-32 wks then terminate pregnancy. O- ve packed cells compatible with mother and fetus given by intraperitoneal or intravascular approach.

23. Prevention of Rh isoimmunisation Administration of Rh anti-D immunoglobulin to mother Dose- 300µg IM following delivery, 100µg IM following abortion,amniocentesis , ectopic preg , mole, APH etc . At 28 weeks to Rh- ve mother if: Father is Rh+ve or father’s Rh status unknown Prior history of causes suggesting feto -maternal bleed Postpartum (within 72 hrs ) if: Rh+ve fetus & DCT – ve After abortion If mother has been sensitized previously, administration of Rh IgG is of no value .

24. 100µg neutralise 5 ml RBC. The no of fetal RBCs in maternal circulation is determined by Kleihauer-Betke (KB) test. The dose of anti-D IgG is based on the result of KB test.

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