Red cell alloimmunization (JUNE 2021)

Red cell alloimmunization (JUNE 2021)

• 1.
  Red Cell Alloimmunization :https://t.me/OBGYN_Note_Book Or https://t.me/Hanybal2021 : https://www.facebook.com/obgyn.books : https://www.slideshare.net/bjlomsecond : https://www.youtube.com/channel/UCXyr7omX- DZ8cTixpQeYvcQ/videos : bjlomsecond@gmail.com
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  Contents Introduction The Rhesus System Prevalence Pathogenesis ScreeningVs Diagnosis Treatment & Management – Unsensitized Mother – First affected pregnancy – Previously affected fetus/infant Intrauterine fetal transfusion Other Treatment Options Special Issues Hemolytic Disease due to non RhD Antibodies
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  Introduction • Rh (Rhesus)factor – named after the monkeys in which it was first discovered – is a RBC surface antigen • Terminology – red cell alloimmunization / sensitization (formerly - isoimmunization) : production of anti RBC antibodies for foreign RBC antigens • Hemolytic disease of fetus & newborn (HDFB) – more appropriate to describe this disorder – Also = erythroblastosis fetalis • Because the peripheral blood smear of these infants demonstrated a large percentage of circulating immature red cells known as erythroblasts – mechanism of fetal anemia • Sequestration & destruction of antibody-coated red cells in fetal liver and spleen 3
• 4.
  Historic Perspectives • Thefirst case of HDFN was probably described by a midwife in 1609 in the French literature • Sir Albert William Liley – a New Zealand medical practitioner – committed suicide in 1983 – major contribution to the story of rhesus disease was the introduction of the fetal intraperitoneal transfusion (IPT) 4 12 March 1929 – 15 June 1983
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  The Rhesus System •The International Society of BloodTransfusion currently recognizes – 33 different blood group systems & 339 red cell antigens • Any individual who lacks a specific red cell antigen may produce an antibody when exposed to that antigen • Two important antigens are common as a cause of transfusion reaction • OAB – most important blood group system – immediate spontaneous agglutinin response • Rh system (6 Rh antigens : C,c,D,d,E,e) – Second most important blood group system – No immediate spontaneous agglutinin response from serum – Two separate genes for the Rh system are found on short arm of chromosome 1 • RHD gene - encodes for D antigen – Rh(D) status described - positive or negative [no d antigen] – Rh Positive—95% (black American), 85% (whites), 100% (in Africans) • RHCE gene, encodes for a combination of CE or ce antigens – Severe fetal anemia requiring antenatal transfusion are due to anti-D, anti-Kell, anti-c, or anti-E alloimmunization 5
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  • Which bloodgroup is Universal Donor?? – Type O- Blood only – Not Type O+ Blood • Incidence: O – 47%;A – 41%; B – 9%;AB – 3% • Du phenotype – Du antigen is manifested by weak expression of the D gene on the RBC envelope – not considered candidates for Rh immunoprophylaxis – Rh Du (+) is considered Rh (D) positive for transfusion 6 • Type A agglutinates only in anti-A • Type B agglutinates only in anti-B • Type AB agglutinates in both • Type O agglutinates in neither of them Determining B/G & Rh
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  • Alloimmunization isuncommon for the following reasons – low prevalence of incompatible red cell antigens; – insufficient transplacental passage of fetal antigens or maternal antibodies; – maternal-fetal ABO incompatibility, which leads to rapid clearance of fetal erythrocytes before they elicit an immune response; – variable antigenicity; and – variable maternal immune response to the antigen 7
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  Prevalence • Incidence ofD positive – varies according to racial and ethnic origin – 85% of non-Hispanic white Americans – 90% for Native Americans – 93% for African Americans and Hispanic Americans – 99% for Asians • Frequency of "Rh-negative" individuals (Medscape) – 6% of blacks; <1% of Asians • With no apparent predisposing factors, fetal RBCs - detected in maternal blood in (ACOG 2018) – 7% of women during 1st trimester, – 16% during 2nd trimester, and – 29% during 3rd trimester • Prevalence of D alloimmunization complicating pregnancy: 0.5 to 0.9% – In population-based screening studies: prevalence of red cell alloimmunization in pregnancy ~ 1 percent 8
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  Incidence of Rhincompatibility (ACOG 2018) • varies by race and ethnicity • Rh negative – 15% of whites • Rh-negative woman has an approximate 85% chance of mating with an Rh- positive man, – 60% of whom are heterozygous and – 40% of whom are homozygous at the D locus – 5–8% of African Americans – 1–2% of Asians and Native Americans 9
• 10.
  D sensitization • WithoutAnti D + ABO-compatible newborn – W 25th: D alloimmunization risk = 16% • 2% will become sensitized by the time of delivery, • 7% by 6 months postpartum, and • 7% will be “sensibilized”—producing detectable antibodies only in a subsequent pregnancy – G 7th: 13% • Without Anti D + ABO-incompatible newborn – D alloimmunization risk = 2% due to erythrocyte destruction of ABO- incompatible cells, which thereby limits sensitizing opportunities • Reduction with prophylactic Anti D – Antepartum (from 16% to 2%) and post partum (from 2% to 0.1%) 10
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  Pathogenesis • Rh incompatibilitycan occur by 2 main mechanisms 1. Exposure to Rh-positive fetal RBCs – The most common type – FMH: abortion (spontaneous/induced), trauma, invasive obstetric procedures, or normal delivery – Grandmother Effect /Theory • D negative female fetus – sensitized by her Rh+ve blood ➔ produce anti-D antibodies even before or early in her first pregnancy ➔ fetus in the 1st pregnancy is jeopardized • As many as ¼ of RhD-negative babies are immunized in early life (G 7th) 2. Rh-positive blood transfusion – blood banks prefer using blood type "O negative" as universal donor in emergency situations • Once sensitization has occurred, it is irreversible – This sensitization may produce immunological memory in the mother for future pregnancies 11
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  • Amount offetal blood necessary to produce Rh incompatibility – as little as 0.1 mL of fetal erythrocytes (ACOG, 2018) • Risk of sensitization depends on – Volume of transplacental hemorrhage – Extent of the maternal immune response – Concurrent presence of ABO incompatibility • Fetal sex may also play a significant role in the fetal response to maternal antibodies – RhD-positive male fetuses (G 7th) • 13 times more likely than their female counterparts to become hydropic • 3 times more likely to die of their disease. • In most cases of red cell alloimmunization, a FMH occurs in the antenatal period or, more commonly, at the time of delivery 12
• 13.
  Maternal antibodies • Aftera sensitizing event, the human antiglobulin anti-D titer can usually be detected after 5 to 16 weeks – Once sensitized, it takes ~ 4 weks for Rh antibodies in the maternal circulation to equilibrate in the fetal circulation – approximately 50% of alloimmunized patients are sensibilized • In this scenario, an antibody screen will be negative, • but memory B lymphocytes are present that can create an anti-D antibody response – With subsequent pregnancy involving an RhD-positive fetus, the antiD titer becomes detectable • In 90% of cases, sensitization occurs during delivery (initial response mostly) can cross placenta – Mostly IgG1 – a non agglutinating antibody that does not bind complement • So no intravascular hemolysis; • Rather sequestration and subsequent destruction of antibody-coated red cells in the fetal liver and spleen → fetal anemia – hemolytic anemia → hyperbilirubinemia → ultimately hydrops fetalis – can’t cross placenta 13
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  • Associated physiologicchanges (G 7th) – Reticulocytosis from the bone marrow (when Hb ↓ by > 2 g/dL) – Erythroblasts are released from the fetal liver (when Hb ↓ by > 7 g/dL) – 2-3 diphosphatidylglycerol (DPG) levels ↑ • In effort to increase oxygen delivery to peripheral tissues – Increased umbilical artery lactate level (when Hb↓ < 8 g/dL) – Increased venous lactate (when Hb 4 g/dL) – Hydrops fetalis - in at least two body compartments (late finding) 14
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  • Immune responseto D antigen - three groups (G 7th) : 60% to 70% • develop an antibody to relatively small volumes of red cells • the probability of immunization increases with escalating volumes of cells • A small percentage of responders can be called hyperresponders in that they will be immunized by very small quantities of red cells : 10% to 20% • immunized only by exposure to very large volumes of cells : 10% to 20% • Totally nonresponders • Sensitization to C, c, E, and e antigens – have lower immunogenicity than the D antigen – complicates ~ 0.3% of pregnancies in screening studies and accounts for about 30% of red cell alloimmunization cases – Anti-E alloimmunization • most common, but the need for fetal or neonatal transfusions is greater with anti-c alloimmunization than with anti-E or anti-C 15
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  Alloimmunization to MinorAntigens • Kell antigens - the most frequent – 90% of non-Hispanic white Americans and up to 98% of African Americans are Kell negative – nearly 90% result from transfusion with Kell-positive blood (so transfusion history is important) – may develop more rapidly and may be more severe than with sensitization to D – mechanism of fetal anemia - differs somewhat from that in Rh-D • anti-K antibodies cause suppression of fetal erythropoiesis rather than due to hemolysis – In one study, a critical anti-K titer of 1:32 support as a predictor of disease severity • Most cases of sensitization to minor antigens result from incompatible blood transfusions • few blood group antigens pose no fetal risk (does not cause fetal hemolysis) – Lewis antibodies - Lea and Leb, as well as I antibodies, are cold agglutinins • They are predominantly IgM and are not expressed on fetal red cells – Duffy group B - Fyb 16
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  Determining Fetal Risk •Up to 40% of D-negative pregnant women carry a D-negative fetus • presence of anti-D antibodies reflects maternal sensitization – but does not indicate whether the fetus is D positive – If a prior sensitization → higher titer despite fetal D status • Chorionic villus sampling (CVS) is not recommended – Due to greater risk for FMH & subsequent worsening of alloimmunization • Fetal testing for other antigens – E/e, C/c, Duffy, Kell, Kidd, and M/N - is also available Fetal BloodTyping • Ultrasound-directed cordocentesis – disruption of the chorion villi during the procedure can result in FMH and a rise in maternal titer, thereby worsening the fetal disease • Amniocentesis for DNA testing – Invasive • ccffDNA: Circulating cell-free fetal DNA 17
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  Rh positive father •Homozygous father (45%) – all of his children will be Rh positive • Heterozygous father (55%) – Children: 50% chance of being Rh positive • By way of contrast the Rh-negative individual is always homozygous 18 Circulating free DNA (cfDNA)
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  ccffDNA: Circulating cell-freefetal DNA • Early studies in pregnant women carrying a male fetus indicated that – 3% of ccffDNA in the maternal circulation in the first trimester is fetal in origin; – this increases to 6% by the third trimester • Source of this DNA appears to be • Noninvasive assessment: sample from maternal plasma after 10 weeks for PCR • can be performed with reliable results at as early as 10 weeks’ gestation • Sensitivity > 99, specificity > 95%, and P/N PPV - very high • Indications – ACOG: does not recommend routinely (Since it is costly) – To identify fetuses that are D Negative and do not require anemia surveillance, and – To withheld anti-D immune globulin if the fetus is D negative • Fetal DNA is rapidly cleared from the maternal circulation with a mean half-life of 16 minutes after cesarean delivery; after vaginal delivery, – fetal free DNA is cleared by 100 hours 20
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  Fetomaternal Hemorrhage • alarge blood loss & true fetomaternal hemorrhage is rare – In one series of > 30,000 pregnancies, • FMH ≥150 mL occurred in 1 per 2800 births • Prevalence of FMH of – at least 30 mL of fetal blood (which can be covered by a standard 300-μg dose of anti-D immune globulin) • is estimated to occur - 3 per 1000 pregnancies – in > 80 percent of cases, no cause is identified 21
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  ABO blood groupincompatibility • Incompatibility for antigens A and B - most common cause of hemolytic disease in newborns, – but it does not cause appreciable hemolysis in the fetus • ~ 20% of newborns have ABO blood group incompatibility – yet only 5 percent are affected clinically (mild anemia) • often seen in firstborn neonates • Rarely becomes more severe in successive pregnancies • considered a pediatric disease - rarely of obstetrical concern – because most anti-A and anti-B antibodies are IgM and do not cross the placenta. – Fetal red cells also have fewer A and B antigenic sites than adult cells and are thus less immunogenic • No need fetal surveillance and early delivery • neonatal observation for hyperbilirubinemia - ? phototherapy CDE incompatibility • Seen in successive newborns • More severe in successive pregnancies • obstetrical concern • fetal surveillance and early delivery is mandatory if mother is sensitized 22 Differences in ABO & CDE incompatibility
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  Screening Vs Diagnosis •Screening – Blood type: ± D antigen? – Antibody screen: • Coombs test (  maternal blood &  fetal/neonatal blood) – Rosette Test (Fetal RBC Screen [Qualitative]) – Kleihauer-Betke test • Diagnostic – Sonography: • MCA peak systolic velocity (most accurate predictor) • Hydrops (ominous finding) – CTG: sinusoidal FHR pattern 23
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  Coombs test Indirect • Forprenatal detection of Rh Antibodies • Take maternal blood → serum → then • In a test tube: – Maternal serum + Animal/human Rh+ve RBCs + coombs reagent (antihuman globulin) → if – Agglutination: mother has produced antibodies against fetal Rh +ve RBCs • -ve (No Agglutination): Give Anti D • +ve (Agglutination): No need to give Anti D – determine antibody titers – critical titer:The level at which significant fetal anemia could potentially develop • Usually ranges between 1:8 and 1:32 • If the critical titer for anti-D antibodies is 1:16, a titer ≥1:16 indicates the possibility of severe hemolytic disease • Exception → Kell sensitization • Kell sensitization – since there is less hemolysis, and severe anemia may not be predicted by the maternal Kell antibody titer • Ancillary tests that should follow titer – Paternal Genotype – Fetal Genotype:Amniocentesis is the primary modality (PCR) • 2 mL of amniotic fluid. • sensitivity and specificity - 98.7% and 100 • Positive and negative predictive values of 100% and 96.9% • in 2nd trimester with > 99% accuracy Direct • To detect anemia 20 to Hemolytic disease of the newborn • Take fetal blood → serum → then • In a test tube mix this serum with coombs reagent → if – Agglutination: neonate’s blood has Abs from mother destroying its blood 24
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  The RosetteTest • AQualitative (not quantitative) test • the initial test of choice, is highly sensitive in qualitatively detecting 10 mL of fetal whole blood in the maternal circulation • To identify quantity of fetal RBC in maternal circulation Technique – Take maternal blood → add anti D (binds to D positive RBCs, but doesn’t agglutinate them) → add indicator RBC bearing D-antigen to form rosette ➔ count number of rosette ➔ • Thus, if rosettes are visualized, there are fetal D- positive cells in that sample • Results interpretation – Negative: result warrants administration of a standard 300 µg dose of RhIG – Positive →Kleihauer-Betke acid-elution test - for quantifying FMH 25
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  Quantitative Tests Kleihauer-Betke acid-elutiontest • the most widely used confirmatory test for quantifying FMH • inexpensive and requires no special equipment – it lacks standardization and precision, and may not be accurate in conditions with elevated F-cells • Principle: fetal hemoglobin (HbF) is resistant to acid-elution whereas adult hemoglobin is acid- sensitive • Technique – smears are prepared from maternal capillary / venous blood → Ehrlich's acid hematoxylin → examined under light microscopy – fetal erythrocytes appear red and adult erythrocytes appear as “ghosts” – fetal cells are then counted and expressed as a percentage of adult cells FMH (ml) = KB % X Estimated maternal blood volume (usually 5000 ml) RhIG vial = (Calculated FMH (ml) ÷ 30 ml) • used for calculating qty o FMH & determining dose o anti D • two scenarios in which it may not be accurate: – Maternal hemoglobinopathies such as β- thalassemia in which the fetal hemoglobin level is elevated and – pregnancies at or near term, when the fetus has already started to produce hemoglobin A Anti-HbF flow cytometry • is a promising alternative, although its use is limited by equipment and staffing costs 26
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  MCA Doppler Velocimetry(PSV) • for detection of fetal anemia • anemic fetus shunts blood preferentially to the brain to maintain adequate oxygenation – So velocity rises because of increased cardiac output and decreased blood viscosity • MCA peak systolic velocity – ≤ 1.5 MoM ➔ begin antenatal testing at 32 weeks • A value > 1.5 MoM for the corresponding GA predicts moderate to severe fetal anemia with a sensitivity of 88% and a negative predictive rate of 89% • Deliver at 37 – 38 weeks – > 1.5 MoM ➔ check fetal Hct by fetal blood sampling • sensitivity of 100% and a false-positive rate of 12% (ACOG 2018) • < 30%  < 35 wk → IUT and for ≥ 35 wk → Deliver • ≥ 30% → begin antenatal testing at 32 weeks → Deliver at 37 – 38 weeks • false positive rate of MCA PSV increases significantly beyond 34 - 35 weeks (ACOG 2018) – due to the normal augmentation in cardiac output that develops at this gestational age 27
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  28 • Circle ofWillis begins to form when the right & left internal carotid artery enters the cranial cavity and each one divides into two main branches: the anterior cerebral artery (ACA) and middle cerebral artery (MCA) • Importance: to provide collateral blood flow bn anterior & posterior circulations of the brain, protecting against ischemia in the event of vessel disease or damage in one or more areas Anterior circulation: From the bilateral internal carotid arteries • supplies most of the cerebral hemispheres (frontal lobes, parietal lobes, lateral temporal lobes and anterior part of deep cerebral hemispheres) Posterior circulation: from bilateral vertebral arteries • Supplies brainstem, cerebellum, occipital lobes, medial temporal lobes and posterior part of the deep hemisphere, mainly the thalamus
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  • The Dopplergate is then placed in the proximal MCA where the vessel arises from the carotid siphon – Measurements in the more distal aspect of the vessel will be inaccurate because reduced peak velocities will be obtained • fetus should be in a quiescent state – because accelerations of FHR can result in a decrease in the PSV, especially late in 3rd trimester • administration of antenatal steroids – decreases in the peak MCA velocity – effect usually lasts for 24 to 48 hours after the last dose • MCA measurements can be obtained reliably as early as 18 weeks’ gestation • Values should be converted to MoM using Internet based calculators (e.g., www.perinatology.com) 29 Correct determination of the fetal peak middle cerebral artery Doppler velocity Techniques – First locate anterior wing of sphenoid bone at the base of the skull → using Color or power Doppler, locate MCA – Angle of insonation is maintained as close to zero
• 30.
  Amnionic Fluid SpectralAnalysis • This test is included for historical interest – demonstrated by Liley (1961) • Amnionic fluid bilirubin concentration – indirect indication of the degree of fetal hemolysis – measured by a spectrophotometer (represented as change in optical density absorbance at 450 nm = ΔOD450) • likelihood of fetal anemia – 3 zone (by plotting the ΔOD450 value) – zones roughly correlated with fetal hemoglobin concentration (anemia severity) – The original Liley graph • valid from 27 to 42 weeks’ gestation – Modified by Queenan (1993) • include gestational ages as early as 14 weeks • NB: amnionic fluid bilirubin level is normally high in mid pregnancy, limiting the reliability of this technique • Currently replace with MCA PSV – Due to its less accuracy & invasiveness 30 • Liley Curve – Zone I – fetus very low risk of severe fetal anemia – Zone II – mild to moderate fetal hemolysis – Zone III – severe fetal anemia with high probability of fetal death 7-10 days • Liley good after 27 weeks • 98% sensitive for detecting anemia in upper zone 2/ zone 3
• 31.
  Percutaneous umbilical bloodsampling (PUBS) • also known as – cordocentesis or funipuncture • associated with a > 4-fold ↑ in perinatal loss compared with amniocentesis • fetal blood type, hematocrit, direct Coombs test, reticulocyte count, and total bilirubin • Although serial PUBS was once proposed as a primary method of fetal surveillance after a maternal critical titer is reached, it has been associated with – a 1% to 2% rate of fetal loss and – up to a 50% risk for FMH with subsequent worsening of the alloimmunization • For these reasons, FBS is reserved for patients with elevated peak systolic MCA Doppler velocities 31
• 32.
  Hydrops fetalis • isdefined as the presence of extracellular fluid in at least two fetal compartments • When hydrops is present, fetal hemoglobin deficits of 7 to 10 g/dL from the mean hemoglobin value for the corresponding gestational age can be expected • the early second-trimester fetus can be severely anemic without signs of hydrops 32
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  Treatment & Management •Issue to consider – Status of sensitization – GA – Severity 33
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  Unsensitized Mother • Criteriato provide prophylaxis – Rh-ve Mother – no evidence of anti-D alloimmunization : Indirect – Negative; RosetteTest - Negative • Omit prophylaxis & screening at 28 weeks – if biologic father: certainly D-negative – if cell-free DNA suggest D-negative fetus • Mini dose vial (50 µg) - Covers fetal 5 ml of fetal blood (2.5 ml of fetal RBC 34
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  1st Dose: atapproximately 28 weeks’ gestation: 300 µg • 1 full dose = 300 µg (1500 IU): Covers fetal 30 ml of fetal blood (15 ml of fetal RBC, since Hct is 50%) • Reduces risk from 16% (ABO compatible newborn) to 2% or from 2% (ABO incompatible newborn) to 0.1% • If both antepartum & postpartum: risk of alloimmunization is reduced to 0.1% [Current 12th] • repeat antibody screening is recommended to identify individuals who have become alloimmunized (AAP, 2017). • Duration: Suppression of Rh isoimmunization: ~ 12 weeks • If > 12 weeks have elapsed since anti-D immunoglobulin administration, consideration should be given to administering 300 µg of anti-D immunoglobulin at 40 weeks of gestation 35
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  2nd Dose: afterdelivery if the newborn is D-positive • given within 72 hours (some protection up to 28 days postpartum ) • If delivery occurs < 3 weeks from the administration of RhIG used for antenatal indications such as external cephalic version, a repeat dose is unnecessary unless a large FMH is detected at the time of delivery • Failed prophylaxis after the appropriate dose of RhIG is rare • anti-D antibody screen may remain positive for up to 6 months. – may produce a weekly positive 1:1 to 1:4 indirect Coombs titer in the mother – Persistence after 6 months is likely to be the result of sensitization 36
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  Anti D Immunoglobulin(Pregnancy risk factor: C) • used to prevent hemolytic disease of the fetus and newborn • Anti-D is a polyclonal IgG product purified from the plasma of D alloimmunized individuals • Half life of RhIG is approximately 16 days • Mechanism of action - Unproven – Possibilities • rapid macrophage-mediated clearance of anti-D-coated red cells and/or • down-regulation of antigen-specific B cells before an immune response occurs • Its MoA in Rx of ITP – Not completely characterized – Rho(D) immune globulin is thought to form anti-D-coated red blood cell complexes which bind to macrophage Fc receptors within the spleen → blocking or saturating the spleens ability to clear antibody-coated cells, including platelets – In this manner, platelets are spared from destruction • Risks – Infection: hepatitis C virus, human immunodeficiency viruses, hepatitis B virus, and parvovirus B19 – Allergic reaction – Serious adverse reactions are rare 37
• 38.
  Formulations prepared by •Cold ethanol fractionation and ultrafiltration – must be administered IM – because they contain plasma proteins that could result in anaphylaxis if given intravenously – Two products: RhoGAM & HyperRho • Using ion exchange chromatography – may be administered either IV or IM – This is important for treatment of significant fetomaternal hemorrhage – two products:WinRho-SDF & Rhophlac • Both preparation methods effectively remove viral particles, including hepatitis and human immunodeficiency viruses 38
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  39 Special Fetomaternal RiskStates Condition & anti D dose Risk of sensitization Remark Abortion o 1st trimester = 50 µg o 300-µg (usually) • 2% - spontaneous • 4-5% - induced o A dose of 50 µg of RhIG is effective until 13 wk due to small volume of RBCs in the fetoplacental circulation Amniocentesis, chorionic villus sampling: 300 µg • 11% o procedures are performed in the unsensitized patient Antepartum bleeding: 300 µg o If there is evidence of a subchorionic hematoma or placenta abruption o If the pregnancy is carried > 12 weeks from the time of RhlgG administration, a repeat prophylactic dose is recommended External cephalic version: 300 µg o Fetomaternal hemorrhage occurs in 2 - 6% of patients Delivery With extensive FMH o Quantify dose based on KB test estimation o occurs in ~ 0.4% of patients o in 2 – 3 per 1000 pregnancies, the volume of FMH exceeds 30 mL of whole blood (ACOG, 2017) o No > 5 vial RhIG should be administered by the intramuscular route in one 24-hour period o Doses of up to 600 µg (3000 IU) can be given 8 hourly till total dose has been achieved o The rule of thumb should be to administer RhIG when in doubt, rather than to withhold it
• 40.
  Classification of Indicationsfor RhIG A = high  Spontaneous miscarriage  Elective abortion  Ectopic pregnancy  Genetic amniocentesis  Chorion villus biopsy  Fetal blood sampling (FBS)  At 28 weeks’ gestation unless father of fetus is RhD negative  Amniocentesis for fetal lung maturity  Within 72 hours of delivery of an RhD positive infant B = moderate  Hydatidiform mole C = low  Threatened miscarriage  Placenta previa with bleeding  Suspected abruption  Intrauterine fetal demise  Blunt trauma to the abdomen  External cephalic version  After administration of RhD-positive blood component 40 LEVEL OF EVIDENCE: A, B, C
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  • Volume ofRhoGAM injected (ml) • (ml of whole blood transfused) (HCT of donor blood) • Volume (ml) of packed RBCs each ml of RhoGAM will “neutralize”, based on the “rule of thumb” ratio of 20 µg of anti-Rho(D)/ml of Rh-positive red blood cells 41
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  First affected pregnancy •~ 25 to 30% of fetuses from D- alloimmunized pregnancies will have mild-to-moderate hemolytic anemia – And without treatment, up to 25 percent will develop hydrops • Management of 1st alloimmunized pregnancy is individualized and may consist of  Determine antibody titers at 20 weeks – titer < critical value → titer is repeated every 4 weeks till 24th wk → every 2 wk – titer ≥ critical value → no benefit to repeating it ➔ US (hydrops), MCA PSV & ? IUT • Doppler @ circle ofWillis & blood flow in the proximal third of MCA • PSV > 1.5 multiples of the median - severe fetal anemia  MCA peak systolic velocity: 1.5 MoM – MCA-PSVs <1.5 MoMs → induce labor at 37 to 38 weeks of gestation – MCA-PSV ≥1.5 MoM → severe anemia → management depends on gestational age • < 35 weeks: fetal blood sampling → if fetal hematocrit <30 percent (< 2 SD) IUT • 35 to 37 weeks: amniocentesis to assess fetal lung maturity → – If matured induce labor (CD for obstetrical indication) – If immature & reassuring BPP → continue to monitor fetal well-being and delay delivery until fetal lung maturity is likely  Fetal blood sampling (Fetal HCT)  Gestational age  Amnionic fluid bilirubin (Currently not used) 42
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  43
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  • No needof serial fetal surveillance – In cases of a heterozygous paternal phenotype or questionable paternity → ccffDNA testing should be sent to a DNA → RhD negative paternal blood or fetal RHD negative genotype • serial fetal surveillance indicated – If - RHD positive fetus, homozygous paternal phenotype or RHD positive fetus by DNA testing • When is the best time to deliver the infant of an alloimmunized patient? – Mild fetal hemolysis • induction of labor at 37–38 weeks of gestation – Severely sensitized pregnancies requiring multiple invasive procedures • Weigh risk of continued cord blood sampling and transfusionsVs neonatal risks associated with early delivery • delivery at 32–34 weeks of gestation after maternal steroid administration to enhance fetal pulmonary maturity 44
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  Previously affected fetus/infant •The management of the second (or more) affected pregnancy is similar, except maternal antibody titers are not helpful in following the degree of fetal anemia – Because maternal titers are not predictive of the degree of fetal anemia – after a first affected pregnancy, future pregnancies tend to manifest with more severe disease and at an earlier gestational age • No need of antibody titers – the pregnancy is assumed to be at risk regardless of titer – because fetal surveillance is indicated by the history of prior affected fetus • a prior pregnancy in which fetal transfusions were required, • a prior stillbirth related to alloirnmunization, or • a prior neonate who required exchange transfusion after delivery 45
• 46.
  • measure MCA-PSVweekly, beginning at 16 to 18 weeks gestation – Serial every 1 to 2 weeks • In the case of a heterozygous paternal phenotype or questionable paternity, ccffDNA analysis to determine the fetal RHD status is indicated. • Amniocentesis – to determine fetal genotype when father is heterozygous for D ➔ • Fetus with D antigen - at risk of hemolytic disease and severe anemia regardless of maternal antibody titers – MCA PSV initiated at 18 weeks → repeated every 1-2 weeks • Fetus with no D antigen: No risk of hemolytic disease – Amniocentesis can be used after 15 weeks’ gestation to determine the status of the fetal red cell antigen in cases of other maternal antibodies such as anti-Kell 46
• 47.
  • Ultrasound parametersthat could predict the early onset of anemia – enlargement of fetal liver and spleen – Since these are sites of extramedullary hematopoiesis and the destruction and sequestration of sensitized red cells in cases of severe HDFN • Both splenic perimeter and hepatic length correlate with the degree of fetal anemia – increased cardiac output • in an effort to enhance oxygen delivery to peripheral tissues – Lower blood viscosity • ➔ produces fewer shearing forces in blood vessels increased blood velocities 47
• 48.
  • Results ofMCA Dopplers will place the fetus into 1 of 3 categories: – normal MCA Doppler – Repeat doppler study every 2 weeks – Delivery - at term or near term (after fetus has achieved pulmonary maturity. – MCA PSV nearing 1.5 MoM – Repeat every 1-2 weeks – Delivery - may be before term & as soon as pulmonary maturity is reached. – Sometimes enhancement of pulmonary maturity by use of corticosteroids may be necessary. – MCA PSV > 1.55 MoM or frank evidence of hydrops {ascites, pleural or pericardia! effusion, subcutaneous edema) – Delivery – when fetus reach a GA at which delivery and neonatal risks are fewer than the risks of in utero therapy 48
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  • If thefetus is preterm – Determine fetal HCT • cordocentesis or percutaneous umbilical cord blood sampling (PUBS) • Intrauterine transfusions (IUT) – between 18 and 35 weeks – Before 18 weeks, access to the umbilical vein is limited due to the small caliber of the vessel – After 35 weeks, the risk/benefit ratio favors delivery of a fetus with evidence of severe anemia – After transfusion, • repeat transfusions or delivery usually will be necessary, as production of fetal blood markedly decreases or ceases • Timing of these transfusions may be assisted by MCA Doppler studies • Delivery should take place when the fetus has documented pulmonary maturity 49
• 50.
  Intrauterine fetal transfusion •Indication - fetal anemia – Peak MCA velocity ≥1.5 MoM and Fetal hematocrit ≤30% • Begin antenatal testing at 32 weeks • Deliver by 37-38 weeks • performed prior to 34 to 35 weeks • women who have undergone several fetal transfusions are given oral phenobarbital for 7 days prior to delivery to enhance fetal hepatic maturity – Phenobarbital: enhance the capability of the neonatal liver to conjugate and eliminate bilirubin – Oral phenobarbital (30 mg TID) for 10 days • decrease the need for neonatal exchange transfusions for hyperbilirubinemia by 75% 50
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  • Target hematocrit –In a nonhydropic fetus - 40 to 50% • Severely anemic fetuses – in the early second trimester do not tolerate the acute correction of their hematocrit to normal values – less blood is transfused initially, and another transfusion may be planned for approximately 2 days later. • initial hematocrit should not be increased by > 4X at the time of the first procedure • A repeat IUT is then performed within 48 hours to correct the fetal hematocrit into the normal range • Before transfusion, a paralytic agent may be given to the fetus – Vecuronium - 0.01 mg/kg administered into the umbilical vein – Fentanyl (2 to 3 µg/kg EFW) can also be used and can be mixed with the vecuronium – Paralysis is almost immediate and lasts 2 to 3 hours • Subsequent transfusions usually take place every 2 to 4 weeks, depending on the hematocrit 51
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  • Route – Intravasculartransfusion • into the umbilical vein under sonographic guidance – Puncture UV in the portion of umbilical cord near its insertion into the placenta • preferred method of fetal transfusion – Intraperitoneal transfusion • may be necessary with severe, early-onset hemolytic disease in the early second trimester, a time when the umbilical vein is too narrow to readily permit needle entry • With hydrops, although peritoneal absorption is impaired, some prefer to transfuse into both the fetal peritoneal cavity and the umbilical vein • In the case of – Anterior placenta • needle is passed through the placental mass into the cord root – Posterior placentation • the cord insertion into the placenta is preferred because this represents a site of immobility compared with a “floating” loop of cord – A sample of fetal blood is obtained for an initial hematocrit 52
• 53.
  • Red cellstransfused are o Type O o D negative o Cytomegalovirus-negative o Washed and packed to a final hematocrit of approximately 75% to 80% to prevent volume overload in the fetus o Irradiated to prevent fetal graft-versus-host reaction o Leukocyte poor • Leukoreduced PRBCs should be used in all neonatal transfusions because it reduces febrile non- hemolytic transfusion reactions, prevents alloimmunization, and reduces the transmission of certain infections (notably CMV) (Grade 2C) • irradiated RBCs - prevent transfusion-associated-graft-versus-host disease • The patient is admitted to the labor and delivery unit as an • skin is prepped with hexachlorophene, and sterile drapes are applied • A 20 gauge procedure needle (a 22-gauge needle is used for gestations <22 weeks) is introduced into the amniotic cavity and then into the umbilical vein under continuous ultrasound guidance 53
• 54.
  Methods to EstimateVolume transfused •Method 1 – (Transfusion coefficient) X EFW • Method 2 – The fetoplacental volume (mL) is calculated from the ultrasound estimate of the fetal weight according to the formula = (1.046 + EFW in grams x 0.14) 54 Target - beginning HCT = Desired increment in HCT Transfusion coefficient 10 0.02 15 0.03 20 0.04 25 0.05 30 0.06 Transfusion coefficient for calculating transfusion volume for fetal transfusion
• 55.
  • MCA peaksystolic velocity threshold for severe anemia – is higher following an initial transfusion • 1.70 MoM rather than 1.50 MoM • It has been shown to be useful in timing the second IUT • After the second procedure, the MCA Doppler loses its validity in predicting fetal anemia – Why? • It is hypothesized that the change in threshold compensates for the contribution of donor cells in the initial transfusion, because donor cells (from adults) have a smaller mean corpuscular volume • Alternately, the timing of subsequent transfusions is based on anemia severity and posttransfusion hematocrit • Following transfusion, the fetal hematocrit generally drops by approximately 1% per day – A more rapid initial decline may be encountered in the setting of fetal hydrops 55
• 56.
  Outcomes • Complications fromIUT are uncommon • overall survival rates exceeding 95 percent – G 7th: overall survival rate of 91% • Procedure-related complications – Fetal death: 2 percent, • stillbirth rate exceeds 15% if transfusion is required before 20 weeks • Considering that fetal transfusion is potentially lifesaving in severely compromised fetuses, these risks should not dissuade therapy. – need for emergent cesarean delivery in 1 percent, and – infection and preterm rupture of membranes in 0.3 percent • Survival rate approached 75 to 80 percent – in nearly two thirds with resolution of hydrops following transfusion, more than 95 percent survived – survival rate was <40 percent if hydrops persisted • Long-term outcomes – more than half - required exchange transfusion in the neonatal period – Few (4.8%) - severe impairments: developmental delay, cerebral palsy & deafness 56
• 57.
  NeonatalTransfusions • prolonging thegestation of the treated fetus with HDFN until near term has resulted in a virtual absence of the need for neonatal exchange transfusions • if cord blood at delivery is submitted for neonatal red cell typing – O-ve reflecting antigen status of the donor blood used for the IUTs • Top up transfusions (simple transfusions) – Most blood transfusions involve adding blood or blood products without removing any blood – Due to: • Elevated levels of circulating maternal antibodies in the neonatal circulation and • Conjunction with suppression of the fetal bone marrow production of red cells – this occurs in approximately 50% of infants near 1 month of age • Supplemental iron therapy in these infants is unnecessary – because there is excess levels of stored iron due to previous hemolysis in utero and lysis of red cells from the IUTs – Supplemental folate therapy (0.5 mg/day) should be considered 57
• 58.
  Other Treatment Options •Maternal plasmapheresis (Gabbe 7th ) – Perinatal survival rate of 69% – Plasmapheresis is started at 12 weeks’ gestation and repeated three times in that week. – The maternal titer should be expected to be reduced by 50%. • Intravenous immune globulin (IVIG) (Gabbe 7th ) – has also been used effectively as the sole antenatal treatment for HDFN – given to replace the globulin fraction removed by plasmapheresis in the form of a 2 g/kg loading dose after the 3rd plasmapheresis; • this is followed by 1 g/kg/week of IVIG until 20 weeks’ gestation FutureTherapeutic Options • Patients with – High anti red cell titers and recurrent perinatal loss in the second trimester have few options • Artificial insemination with red cell antigen – negative donor semen • Surrogate pregnancy, or • Preimplantation diagnosis (if the father is heterozygous) • Proteasome inhibitors 58
• 59.
  Special Issues 59 Special Issues ConditionRemark Positive titer at delivery • After dose at 28th week, low titer at term (≤4) may exist, still give anti D if infant is D-positive • But, if IgM antibody is present or IgG titer >1:4 - alloimmunization is proven D positive mother at delivery • Large FMH ? → KB test / flow cytometry and to determine the appropriate dose of anti-D immunoglobulin • See prior D antigen typing Inadvertently omitted Anti-D • Give as soon as possible after recognition of the omission • Partial protection is afforded with administration within 13 days of the birth or potentially sensitizing event, and some experts recommend giving it as late as 28 days anti-D given shortly before delivery • Women who deliver < three weeks from the administration of anti-D immunoglobulin for the usual indications do not require a post partum dose (unless a large FMH ) Postpartum sterilization procedures • Controversial • ACOG considers women undergoing postpartum sterilization procedures candidates for anti-D immune globulin
• 60.
  60 Special Issues Condition Remark Womenundergoing intraoperative cell salvage • maternal blood sample should be obtained 30 to 45 minutes after reinfusion to estimate the volume of fetal red cells in the maternal circulation in case more anti-D immunoglobulin is indicated False-positive anti-D antibody screen • a typical D-sensitized patient, the anti-D antibody titer exceeds that of anti-C antibody • If the anti-C titer equals or exceeds the anti-D titer, the clinician should consider the possibility that the anti-D antibody is actually anti-G antibody • G antigen is present on almost all D+ or C+ cells and absent from virtually all red cells which lack D and C antigens.Anti-G antibody serologically mimics a combination of Anti-C and Anti D.The challenge of anti G in the antenatal setting is to identify whether Anti D is present or not Weak / discordant D typing • treated as negative & provide antenatal and postpartum anti – D • For the purposes of • blood donation, they are categorized as D positive • transfusion recipients with weak D are considered D negative Inadvertent administration of anti-D to a +ve woman • not harmful
• 61.
  61 Special Issues Condition Remark pregnancieswith severe fetal anemia before 20 wk • intrauterine transfusion - mainstay of treatment, • Plasma exchange and administration of IVIG women with multiple antibodies • no specific guidelines • warrant close observation Prevention of an affected fetus in future pregnancies • Avoid conception of an Rh(D)- positive fetus – with following methods 1. In vitro fertilization (IVF) with preimplantation genetic diagnosis 2. Use of a gestational surrogate 3. Use of donor sperm from an Rh(D)-negative donor IVF/donor egg/surrogacy • Management of pregnancies involving a donor gamete or a gestational surrogate is based on • the predicted antigen status of the fetus and • the known antibody status of the gestational carrier
• 62.
  Hemolytic Disease dueto non RhD Antibodies • antibodies to minor antigens occur in 1.5–2.5% of obstetric patients • Most cases of alloimmunization due to these minor antigens are caused by incompatible blood transfusion • antibodies to > 50 other red cell antigens have been reported to be associated with HDFN – only three antibodies • anti-RhD, antiRhc, and anti-Kell (K1) ➔ cause significant enough fetal hemolysis that treatment with IUT is considered necessary • In one series from a tertiary care center for IUT in the Netherlands, – 85% of cases involved anti-D; – 10%, anti-K1; and – 3.5%, anti-c 62
• 63.
  • care ofthe pregnant patient with antibodies to one of the clinically significant minor antigens is similar to care of Rh-D alloimmunized pregnant women • Exception – alloimmunization to the K or K1 antigens of the Kell blood group system – Kell alloimmunization appears to be less predictable and often results in more severe fetal anemia than alloimmunization due to other erythrocyte antigens. – mechanism of anemia due to Kell alloimmunization to be different than with Rh- D alloimmunization • So maternal Kell antibody titers and amniotic fluid ΔOD450 values are not as predictive of the degree of fetal anemia as with Rh-D sensitization • Doppler measurements, however, appear to be accurate in predicting severe fetal anemia 63
• 64.
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