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DR.E.ZAREAN
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First demonstrated by testing human blood with rabit anti sera against red cells of Rhesus monkey & classifying Rh negative & Rh positive. However the underlying biochemical genetics is not well understood and the genotyping & phenotyping remains little confused. The genotype is determined by the inheritance of 3 pairs of closely linked allelic genes situated in tandem on chromosome 1 & named as D/d, C/c, E/e (Fisher- Race theory)
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Rh Negative Women Man Rh positive (Homo/Hetero) Fetus Rh Neg Fetus No problem Rh positive Fetus Rh+ve R.B.C.s enter Maternal circulation Mother previously sensitized Secondary immune response ? Iso-antibody (IgG) Non sensitized Mother Primary immune response Fetus unaffected, 1 st Baby usually escapes. Mother gets sensitised? Fetus Haemolysis ?
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Chances of T.P.H/F.M.H. are only 5% in 1st trimester but 47% in 3rd trimester, many conditions can increase the risk. Chances of primary sensitization during 1st pregnancy is only 1-2%, but 10 to 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
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HAEMOLYSIS IN UTEROAFTER BIRTH BILLIRUBIN ANAEMIA MAT. LIV NO EFFECT HEPATIC ERYTHROPOESIS & DYSFUNCTION PORTAL & UMBILICAL VEIN HYPERTNSION, HEART FAILURE BIRTH OF AN AFFECTED INFANT - Wide spectrum of presentations. Rapid deterioration of the infant after birth.May contiune for few days to few months. Chance of delayed anaemia at 6-8 weeks probably due to persistance of anti Rh antibodies. Jaundice Kernicterus Hepatic Failure DEATH ERYTHROBLASTOSIS FETALIS IUD
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Amniocentesis; CVS Threatened abortion, previa, abruption Trauma to abdomen External cephalic version Multiple pregnancies Cesarean delivery Fetal death Percutaneous umbilical blood sampling Manual removal of placenta Hydatidiform mole EP
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Premarital counseling? Ambitious? Blood grouping must for every woman, before 1st pregnancy. Rh+ve Blood transfusion- 300mcg Immunoglobulin (minimum). Proper management of unsensitised Rh negative pregnancies.
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Blood typing at 1st visit, If negative :husband’s typing. If husband is also negative then no treatment If husband is positive, if possible, Homo/Hetero? Do Indirect Coomb’s test of mother – Negative-good. Repeat ICT at 28 weeks – Negative : 300mcg Rh immunoglobulin Positive Sensitised.
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If Rh positive(neonate)- Test mother’s blood for ICT & Infant’s for DCT Negative or weakly reactive- 300mcg immunoglobulin. Positive – Sensitised–Hb & Bilirubin Estimation of the infant -Treat the infant.
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Schedules First trimester - 50 μ g RhIgG Amniocentesis - 300 μ g RhIgG Antepartum bleeding If first trimester - 50 μ g RhIgG If third trimester - 300 μ g RhIgG Postpartum 300 μ g RhIgG
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Causes of sensitization- Misinterpretation of maternal Rh type Rh +ve blood transfusion Unprotected preg. & labour Inadequate dose / improper use of IgG on previous occasions Immunization to cross-reacting antigen
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Careful planning during antepartum, intrapartum & neonatal period Father’s blood type & Rh antigen status Knowledge of maternal antibody titer to the specific antigen Intrauterine foetal monitoring with repeated ultrasound examination, cordocetesis / amniocentesis
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Fetus Rh Negative: - Observation Fetus Rh Positive: - Intrauterine transfusion of ‘Rh Neg’ blood as indicated Timely delivery any time after 32 weeks Management of the infant up to 8 weeks In cases of severely sensitized women, consider medical termination of pregnancy and sterilization.
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Anemia Erythroblastosis fetalis Ascites Heart failure Pericardial effusion
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Maternal antibody titer negative - do serial antibodies If titer low - little risk of anemia If > 1:16 - perform amniocentesis and/or Doppler assessment ∆OD450 plot on Liley curve Zone I - Rh negative or fetus mildly affected Zone II - moderately affected Zone III - high risk for IUFD
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Serial sonograms Early signs Thickened placenta Liver span Increased umbilical vein diameter Increased blood velocities in UV, aorta and middle cerebral artery Severe disease - scan every week if hydropic changes. If hydropic changes, consider fetal transfusion.
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Intraperitoneal : First done in 1963 Instill blood through needle or epidural catheter Volume to transfuse = (G.A.-20) x 10ml Generally, repeat in ~ 10 days, then every 4 wk. Risk of death about 4% per procedure Not effective in hydropic fetus Some advocate combined approach (IPT and IVT)
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Intravascular : Goal is to have post-transfusion Hct 40-45% Can infuse about 10 ml/min Estimate requirement based on EFW and pre-transfusion Hct Repeat in 1 wk., then about every 3 wk. Hct falls about 1%/day Goal: keep Hct > 25% Smaller volumes, therefore more procedures compared to IPT Fetal loss about 1.5% per procedure
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