HDFN Heba Khalid (1) PDF

HDFN : - I chapter 20 Introduction: HDFN is a rare condition that result from RBCs destruction of a fetus and neonate by antibodies...

HDFN : - I chapter 20 Introduction: HDFN is a rare condition that result from RBCs destruction of a fetus and neonate by antibodies produced by the mother. The maternal antibodies that cause HDFN can be either naturally occurring ABO antibodies -(isohemagglutinins), or develop after exposure to foreign RBC; the latter are called blood group - alloantibodies Maternal RBC alloimmunization can be caused by forign previous pregnancy or previous transfusion. Risk - gig Til  Most maternal alloimmunization 83% was due to previous pregnancy , while only 4% was due - to previous transfusion and & 14% was unable to - be determined - Before the advent of Rh immune globulin - - & (RhIG),about 95% of the cases of HDFN were => caused by maternal antibodies directed against the Rh antigen D (RhD). despit I in fregency but & important cause of incompatibility air. Recently, ABO incompatibility has become the - most common cause of HDFN. - fetus RBC inharted from father Ay ↳ attached Ab t produc o Pathogensis A- HDFN caused by ABO ABO antibodies are present in the plasma of all individuals whose RBCs lack the corresponding antigen These antibodies, also called isohemagglutinins, result from environmental stimulus in early life. mother and infant are ABO-incompatible in one in every five pregnancies. Anti-ABO antibodies are predominantly IgM class, which are not effectively transport o the placenta. Maternal ABO antibodies that are (IgG)can cross the placenta and attach to the ABO antigens of the fetal RBCs. ^ Group Oindividuals are most likely to form high-titer IgG anti-ABO antibodies, ABO HDFN is nearly always limited to A or B infants of group O mothers with potent anti- A,B antibodies Epidemiologically, clinically significant ABO HDFN occurs most frequently in group O mothers who have a group A infant in the white populations and group B infants in the black population appears to be more likely when these antibody titers are high (≥512). ABO HDFN can occur in the first pregnancy and in any, but not necessarily all, subsequent pregnancies because it does not depend on previous foreign RBC stimulation. Tetanus toxoid administration and helminth parasite infection during pregnancy have been linked to the production of high-titered IgG ABO antibodies and severe HDFN. The typically mild course of ABO HDFN is related to the poor development of ABO antigens on fetal RBCs. ABO antigens are not fully developed until after the first year of life. Group A infant RBCs are serologically more similar to A2 adult cells, with group A2, infant RBCs much weaker. As expected, group A2, infants are less likely to have ABO HDFN.  - - - - - - - - - - - -- - hydrops Fatalise Kernicterus are extranly rare in ABO induc HIFN FMH Maternal alloimmunization results from exposure to foreign red blood cells through previous or current pregnancy, previous transfusions, or organ transplant. - During pregnancy, there is spontaneous mixing between fetal and maternal circulation (fetal-maternal hemorrhage; FMH) - The mixing increases throughout the pregnancy; 3%, 12%, and 45% in trimesters I, II, and Ill, respectively. Any physical perturbation of a fetus or placenta in utero also increases the risk of FMH, such as trauma, abortion, ectopic pregnancy, amniocentesis, or multiple pregnancy - Maternal factor ; The ability of individuals to produce AB in response to antigenic exposure varies, depend on complex genetic factor In RH -negative individuals who are transfused with 200 Ml of RH positive RBC approximately 85% respond and form anti-D. 15 % non responder ,Nearly all of the nonresponders will fail to produce anti-D even with repeated exposure to RhD-positive blood. If RhIG is not administered to an RhD-negative mother, the risk of immunization is only about 16% after an RhD-positive pregnancy. Immunoglobulin class and subclass of the maternal antibody affects the severity of the HDFN. Of the immunoglobulin classes (i.e., IgG, IgM, IgA, IgE, and IgD), only IgG is transported across the placenta. The active transport of IgG begins in the second trimester and continues until birth The IgG molecules are transported via the Fc portion of the antibodies Of the four subclasses of IgG antibody, IgG1, and IgG3 are more efficient in RBC intravascular hemolysis than are IgG2 and IgG4. All subclasses of IgG are transported across the placenta. RBC antibodies specificity Of all the RBC antigens RhD is the most antigenic. The common antigens in the Rh system (C, E, and c) are also potent immunogens and, anti-E and anti-c can caused severe HDFN that required intervention and treatment. Of the non-Rh system antibodies, anti-Kell is considered the most clinically significant in its ability to cause HDFN. Kell blood group antigens are present on immature erythroid cells in the fetal BM, so severe anemia occurs not only by destruction of circulating RBCs but also by destruction of precursors. bec of impact of Anti-k on fetal RBC precursor ,anti -k titer is less predictive of sever fetal anemia. therfer all Pregnant women with anti-k RBC should be fallowed closely for evidance of HDFN Other antibodies that have been less commonly reported include Kpa, Kpb, Ku, Ge, M, Jsa, Jsb, Jka, Fya, Fyb, S, s, and U.  Antibodies Identified in Prenatal Specimens That Can Cause of HDFN · - - ② - - - ~ ④ - - & - - & - & Influence of ABO Group : When the mother is ABO-incompatible with the fetus (major incompatibility), the incidence of D immunization is less detectable. This apparent protection from RhD immunization is likely due to the clearing and/or hemolysis of ABO-incompatible RhD- positive fetal RBCs in the mother’s circulation before the RhD - antigen can be recognized by her immune system. --- Comparison of ABO Versus RhD HDFN - L - & - - - - - - -  mother immunized to RBC all Ag · once - , offspring subscyentaffectio who inhart A will potentially Hemolysis, Anemia, and Erythropoiesis : The maternal IgG antibody crosses the placenta and binds to the fetal antigen-positive cells - - the antibody-coated cells are removed from the - circulation by the macrophages of the fetal spleen. - - - Destruction of fetal RBCs ( Hemolysis) and the resulting fetal anemia stimulate the fetal Bone - marrow to produce RBCs at an accelerated rate - - even to point that erythroblast are related to circulation - The term erythroblastosis - fetalis was used to describe this finding - Rate of rbc distrustion depends on AB titer and number of antigenic site on feral rbc. When the bone marrow fails to produce enough RBCs to keep up with the rate of RBC destruction, erythropoiesis outside the bone marrow is increased in the hematopoietic tissues of the fetal spleen and liver. These organs become enlarged (hepatosplenomegaly), resulting in portal hypertension and hepatocellular damage. Severe anemia and hypoproteinemia caused by decreased hepatic production of plasma proteins leads to the development of high-output cardiac failure with generalized edema, effusions, and ascites, a condition known as hydrops fetalis. In severe cases, hydrops fetalis can develop by 18 to 20 weeks' gestation. In the past, hydrops tetalis was almost uniformly fatal; today, most fetuses with this condition can be treated successfully, although many suffer permanent consequences. children treated with intrauterine transfusion (IUT, below), tmost likely to have severe long-term neurological impairment. The process of RBC destruction continues after birth as long as maternal antibody persists in the newborn infant's circulation. The rate of RBC destruction after birth decreases because no additional maternal antibody is entering the infant's circulation through the placenta. However, IgG is distributed both extravascularly and intravascularly and has a half- life of 25 days, so antibody binding and hemolysis of RBCs can continue for several days to weeks after delivery.  distribut - * Whoever-Igh both extra-vasular intra Vascular- I has half life of 25 days , So binding shemolysy Pathogenesis of HDFN Ab continu several days wK after delivery. - There are three different phases of anemia caused by HDFN: early (within 7 days of birth) due to antibody mediated - hemolysis - late hemolytic anemia (2 weeks or more after birth) due to - - continued hemolysis , the expanding intravascular - - compartment, and natural decline of hemoglobin levels & - of growing infarct late hypo regenerative anemia due to marrow suppression as - - a result of transfusions and IUT, antibody destruction of RBC - - - - precursors , and deficiency of erythropoietin. - - => ex  Neonatal Manifestations of HDFN- Induced Anemia by Time of Onset - & & & - - - - - -  -unconjugated bilrubin is water insoluble trave o blood stream to liver to Bilirubin: be Conjugated excret (water ~GIT- solubles > - RBC destruction releases hemoglobin, which is metabolized to ② bilirubin in different metabolic stages. During pregnancy, the indirect bilirubin is transported across - - the placenta and conjugated by the maternal liver and safely - - - excreted. & After birth, the immature infant liver cannot yet metabolize bilirubin efficiently, and this leads to the accumulation of unconjugated bilirubin and neonatal jaundice. - Untreated high bilirubinemia due to the pathological RBC brain. ↳ destruction can cause kernicterus or permanent damage to the 2018 - 20 myldl) Diagnosis ; Postnatal Diagnosis No single serologic test is diagnostic for ABO HDFN. When a newborn develops jaundice within 12 to 48 hours after birth, various causes of jaundice need to be investigated. 1-The DAT on the cord or neonatal RBCs is the most important diagnostic test. the DAT result can be positive even in the absence of signs and symptoms of clinical anemia in the newborn infant, (as these infants may have compensated anemia or the RBCs are not being destroyed by the reticuloendothelial system.) Note; Collecting cord blood samples on all delivered infants is highly recommended. The sample should be collected by venipuncture to avoid contamination with maternal blood and Wharton's jelly (the material surrounding the blood vessels) should be anticoagulated for storage. 2-ABO, RhD, testing can be carried out and the results can be assessed. When the DAT result is negative but the infant is jaundiced, other causes of jaundice should be investigated. In the rare cases in which ABO incompatibility can be the only cause of neonatal jaundice, but the DAT result is negative, the eluate of the cord RBCs may reveal ABO antibodies. The eluate can also be helpful when the mother's blood specimen is not available.  perinatal Diagnosis 1__ Detailed maternal history is useful to determine - Q previous pregnancy outcomes, particularly for past - stillbirths or hydropic fetal losses, and potential - - ② etiology of the offending red cell antibody. o transfusion privous bloodf (poor out some outcomeis -priv sudz can predict similar -  In addition, fetal ultrasound to determine gestational age and absence of ascites is indicated - - -  Tests performed to all women at 1st trimester, including a blood type (ABO, RhD) and antibody - detection test (indirect antiglobulin test) that detects - clinicallyIgG antibodies.I that react at 372 1. Signifant - & IAT In at least two separat reagent screening RBL that express all of common blood group Ay,  preferably homozygous 3. Sh. be used. also Ab enhancing media such as polyethylene glycol PEG or LISS can ↑ senstiity of test. zest Certain blood group antibodies such as anti-I, -P1, -Le , and - a - -- s Leb, may be ignored because the corresponding antigens are - ~ - i - incompletely developed at birth, the antibodies are typically not - - clically IgG, and clinical experience has established the rarity of their - in- - causing HDFN. significant - Ab Women with red blood cell sensitization to clinically significant - red cell antigens (such as D, E, c, K, etc) are transitioned into a g & ---- pathway of more intensive diagnostic testing and monitoring. - - who to avoid appearance of clinically insignfant Ab ?! ① immediat Spine & Room temp incubation can be omitted - us , monospastic reagent (ant-Igal rather than polyspasfics  reduce of Ab these steps detection Fyi that can't cross-placenta method than otherAt screening -other IAT) - solid phase column used ga be - may not is non-reactive If Ab screening test befor RhIG therapy in repeat prenatal pts Rh D-negative has been in Grd trimester , If pet he of unexpected transfused or Ab ,  an Antibody Identification If the antibody screen is reactive, the antibody identity must be determined. Bec Follow-up testing will depend on the antibody speciticity. Cold reactive IgM antibodies such as anti-1, anti-IH, anti-Lea, anti-Leb, and anti-P, can be ignored. Lewis system antibodies are rather common in pregnant women but have not been reported to cause HDFN Antibodies such as anti-M and anti-N can be IgM or IgG or a combination of both. Both anti-M and anti-N can cause mild to moderate HDFN, although rarely. Next To establish the immunoglobulin class, the serum can be treated with a sulfhydryl reagent, such as dithiothreitol or 2-mercaptoethanol, and then retested with appropriate controls. The J-chain of IgM antibodies will be destroyed by this treatment; IgG antibodies will remain reactive. Many Rh-negative pregnant women have weakly reactive anti-D, particularly during the third trimester. Most of these women have received RhiG, either after an event with increased risk of tetomaternal hemorrhage or at 28 weeks' gestation (antenatal). The passively administered anti-D will be weakly reactive in testing and will remain demonstrable for 2 months or longer. This must be distinguished from active immunization. A titer higher than 4 almost always indicates active immunization; with a titer under 4, active immunization cannot be ruled out, but it is less likely. Who to resolve this problem? 1- If encountering a sample trom a pregnant patient, using PEG appears to provide the least number of false positives compared to gel cards and solid phase. 2-Communication with the patient's provider to obtain a history of RhiG administration is an important confirmatory step as serological methods alone are not able to determine the derivation of the antibody. If the antibody speciticity is determined to be clinically significant and the antibody is IgG, further testing is re-quired. Other than anti-D, the most common and most significant antibodies are anti-K, anti-E, anti-c, anti-C, and anti-Fya (Table 20-2). Next step Antibody titres Methods used to determine the relative concentration of all AB that capable to cross the placenta and cause HDFN Method The patient serum or plasma is serially diluted and tested against appropriate RBCs to determine the highest dilution at which a reaction occurs. The method must include the indirect antiglobulin phase using anti-IgG reagent. The result is expressed as either the reciprocal of the titration endpoint or as a titer score. Note; 1-The titration must be performed exactly the same way each time the patient's serum is tested. 2- The recommended method is saline antiglobulin tube test, With 60 min incubation at 37 c and use of anti-IgG reagent 3- The RBCs used for each titration should have the same genotype (preferably homozygous for the antigen of interest), approximately the same storage time, and the same concentration. 4-The first serum or plasma specimen should be frozen and run in parallel with later specimens to increase accuracy since the titer test results are difficult to reproduce. Only a difference of greater than 2 dilutions or a score change of more than 10 is considered a significant change in titer. Titration at time of delivery not recommended bec of no clinical useful information WHY Antibody titer alone cannot predict severity of HDFN? In some sensitized women, the antibody titer can remain moderately high throughout pregnancy while the fetus is becoming more severely affected. Similarly, a previously sensitized woman can have consistently high antibody titer, whether pregnant or not ,and whether the - - fetus is RhD-positive or RhD-negative. - - In others, the titer can rise rapidly, which increasing severity of - HDFN. - However, antibody titers consistently below the laboratory’s critical titer throughout the pregnancy reliably predict an unaffected or mild-to-moderately affected fetus, with the exception of anti-K with a K-positive fetus.  Paternal Phenotype and Genotype im A specimen of the father's blood should be obtained and tested for the presence and zygosity (predicted copy number of the gene) of the corresponding blood group antigen to predict fetal risk of being affected by HDFN. Fathers that are homozygous for the blood group gene have a 100% chance of passing this gene to their offspring; heterozygous fathers have a 50% chance. - For most blood group systems, serological testing of the father's blood type is sufficient to predict homozygosity or heterozygosity of the antigen. For instance, anti-K and anti-k antisera can detect K and k antigens, respectively, and provide accurate prediction of the risk that the fetus has inherited the blood group antigen. For RhD, serological testing alone cannot predict the number of RhD genes that the father carries because there is no antithetical allele for the RhD gene. Fetal DNA Testing carried out by obtaining fetal cells through amniocentesis or chorionic vil-lous sampling (CVS) as early as 10 to 12 weeks' gestation. The fetal cells are grown in tissue culture, and then DNA is extracted to determine if the fetus has genes coding for the blood group genes, including RHD and others (c, e, С, Е, K, Fya, Fyb, Jka, Jkb, M). To avoid an invasive procedure, fetal DNA can be isolated from maternal plasma trom a peripheral blood sample to determine RHD and KEL genotype. The cell-free DNA (cDNA) method has advanced fetal risk stratification for mothers with RBC alloimmunization. In some countries cDNA methods are also used when the mother is RhD-negative to determine if the fetus is predicted to be RhD-positive and therefore if RhIG should be adminis-tered,This may be a cost-effective approach.  guants Management of the Fetus During pregnancy, women with known RBC alloimmunization and/or a history of HDFN are: i. Closely monitored using antibody titers. ii. The fetus is also closely monitored throughout the pregnancy to check for fetal wellbeing and fetal anemia and to determine when is the best time to deliver.  1.Fetal Ultrasound At about 16 to 20 weeks’ gestation, done every 2 weeks to track the degree of fetal anemia: the clinical diagnosis of fetal anemia can be made using an ultrasound technique called fetal middle cerebral artery peak systolic velocity (MCA-PSV). Doppler readings that are >1.5 multiples of the mean (MoM) are sensitive enough to predict significant fetal anemia in which intervention may be needed. The measurement is based on the 30 reduced blood viscosity at lower hematocrits and resulting in faster velocity of the blood. 2. Invasive Monitoring : Cordocentesis and Amniocentesis When fetal anemia becomes moderate to severe as indicated by Doppler MoM measurements exceeding, go to invasive technigue. is_ way Cordocentesis is done to determine fetal hematocrit. intrauterine transfusion is indicated if the fetus has hematocrit level is less than 30%sait.at n'hafEEhioy Fetal blood sample can also be tested for bilirubin, ABO, Rh, DAT, and antigen phenotype & genotype. For risk stratification of fetal anemia, amniocentesis to monitor amniotic fluid bilirubin levels has been replaced with MCA-PSV  In the past, the concentration of bilirubin pigment in the amniotic fluid was used to estimate the extent of fetal hemolysis. The amniotic fluid is tested by a spec-trophotometric scan optical density (OD) at 450 nm (the absorbance of bilirubin). The measurement is plotted on a graph (Liley Curve Graph) according to gestational age. An increasing or unchanging AOD 450 nm as pregnancy proceeds predicts worsening of the hemolysis. High values indicate severe and often life-threatening hemolysis (fetal Hb less than 8 mg/dl )and require urgent intervention Currently,amniocentesis used to obtain aminocyte for DNA testing. 3.Intrauterine Transfusion (IUT) : indications: 1. MCA-PSV indicates anemia (>1.5 MoM). 2. Fetal hydrops is noted on ultrasound examination. 3. Cordocentesis blood sample has Hb level less than 10 g/d or HCT less than 30% 4. Amniotic fluid optical density 450 nm results are high and/or increasing. Which indicate increasing level of bilirubin. The goal of intrauterine transfusion is to maintain fetal hemoglobin above 10 g/dL. Characteristics of RBC used for IUI &ET: 1. typically group O 2. RhD-negative (or RhD positive, depending on maternal blood group antibody) 3. leukocyte reduced 4. hemoglobin S negative 5. CMV-safe (CMV seronegative or leukocyte reduced), 6. irradiated The RBC unit is irradiated to prevent TA- GVHD 7. antigen negative for maternal red blood cell antibody/antibodies. 8. The HCT level of the RBCs greater than 70% because of the small volume transfused and the need to correct severe anemia 9. Fresh (to decrease risk of hyperkalemia) Less than 7 10 day from collection Once intrauterine transfusion is initiated, the procedure is typically repeated every 2 to 4 weeks until delivery to suppress fetal hematopoiesis. The initial intrauterine transfusion is rarely performed after 36 weeks' gestation. Cordocentesis, intrauterine transfusion, and amniocentesis have several risks, including infection, premature labor, and trauma to the placenta, which may cause increased antibody titers because of antigenic challenge to the mother through fetomaternal hemorrhage. To protect the mother from additional sensitization due to the exposure to donor RBCs some authors tried to prevent alloimmunization by using Rh C, c, E, e, and K maternally antigen-matched RBCs for IUT, but found that the risk of additional maternal RBC antibodies remained. High-level antigen matching (Duffy, Kidd, Ss) of mothers with HDFN does seem to reduce the risk of further alloimmunization, but the RBCs become increasingly difficult to find and the clinical impact is not clear. Intrauterine transfusion alone carries a 1% to 3% chance of adverse fetal events such as premature rupture of membranes,When done in the early second trimester, the outcomes are poor Despite the risks of IUT, children older than 2 years who were treated with this procedure while in utero had a relatively low rate (4.8%) of neurocognitive impairment (cerebral palsy, severe developmental delay, bilateral deafness, blindness) so long as they were not severely hydropic. Management of the Infant When birth occurs, the connection from the fetal to maternal circulation is severed, and the risk of hyperbilirubinemia increases because the fetal metabolic pathway to metabolize bilirubin is immature. Although many babies are affected with neonatal jaundice,but those with HDFN-induced hemolysis are at greater me risk of the bilirubin reaching very high levels and thus for bilirubin- induced encephalopathy. 1. Cord Blood Testing ABO Grouping: ABO antigens are not fully developed in newborn infants; their RBCs may show weaker reactions with anti-A and anti-B antisera than for older children and adults. In addition infants do not have their own iso hemagglutinins but may have those of the mother, so reverse grouping cannot be used to confirm the ABO group RhD Typing DAT : The most important serologic test for DX HDFN is the DAT with anti-IgG reagent. A positive test result indicates that there is antibody coating the infant’s RBCs.  Rh D typing Rarely, the infant's RBCs can be heavily antibody-bound with maternal anti-D, causing a false-negative Rh type, or what has been called blocked Rh.35 An eluate from these RBCs will reveal anti-D, and typing of the eluted RBCs will show reaction with anti-D. Continue…DAT however, the strength of the reaction does not correlate well with the severity of the HDFN. A positive test result may be found in infants without clinical or other laboratory evidence of hemolysis (e.g., mother received RhIG). 4-Elution The routine preparation of an eluate of all infants with a positive DAT result is unnecessary. Elution in cases of known HDFN and postnatal ABO incompatibility is not needed, because eluate results do not change therapy. The preparation of an eluate may be helpful when the cause of HDFN is in question or suspected. ( the resolution of a case of blocked RhD typing requires an eluate). 2.Exchange Transfusion Exchange transfusion is the use of whole blood or equivalent to replace the neonate’s circulating blood and simultaneously remove maternal antibodies and bilirubin. Exchange transfusion is indicated when levels of bilirubin reach critical levels (which depends on the infant’s gestational age). Exchange transfusion is rarely required because of advances in phototherapy and the use of IVIG. Blood product selection is similar to that of IUT. Bec infant whole blood being replaced,RBC unit should be mixed with plasma unit to creat reconstituted whole blood. After a two-volume exchange transfusion, approximately 90% of the red blood cells have been replaced and 50% of the bilirubin has been removed. After the procedure, a platelet count should be performed to monitor for iatrogenic thrombocytopenia. Process of exchange transfusion 3.Simple Transfusions The infant may receive small-volume or “top-off” RBC transfusions to correct anemia any time from after birth to many weeks later. Infants must be carefully monitored for clinical signs of ongoing anemia, which can be clinically suspected when the infant has poor feeding or increased sleep. When transfused, the RBCs selected have the same attributes as noted with IUT and exchange transfusion. Many hospitals keep 1 unit dedicated to infant with HDFN and draw small aliquots from parent rbc unit overtime to decrease donor exposure over multiple transfusion episodes.  4.Phototherapy Phototherapy at 460 to 490 nm is used to metabolize the unconjugated bilirubin to isomers that are less lipophilic, less toxic to the brain, and able to be excreted through urine..For infants with mild to moderate hemolysis or history of intrauterine transfusion, phototherapy is generally sufficient to adequately conjugate the bilirubin and lessen the need for transfusion. 5. Intravenous Immune Globulin IVIG is used to treat hyperbilirubinemia of the newborn caused by HDFN. The IVIG competes with the mother’s antibodies for the Fc receptors on the macrophages in the infant’s spleen, reducing the amount of hemolysis. IVIG appears to reduce the need for exchange transfusions and phototherapy, but it does not affect the need for top-off transfusions. Prevention Prevention of HDFN can be divided into primary and secondary measures. Because there are no international standards, nations differ on preventative measures for HDFN, including dosing and dosing schedules of RhIG and the approach to RBC transfusion.  prevention a - Selection of RBCs for Females: 1. preserve RhD negative RBCs in the blood bank inventory for use for women of childbearing potential. This is entirely in place to reduce the risk of RhD sensitization and of HDFN affecting future pregnancies. 2. minor blood group antigens are matched for women of childbearing potential. 3. use K-negative RBC units for women younger than 45 to 50 years of age. 4. additional matching for antigens such as c and E. 83% of maternal sensitization that went on to cause severe HDFN was due to previous pregnancy and not transfusion itself. Rh Immune Globulin: The risk of an RhD-negative mother becoming allosensitized can be reduced from 16% to less than 0.1% by the appropriate administration of RhIG. The mechanism of action of RhIG is uncertain. Evidence indicates it interferes with B-cell priming to make anti-D, although other modes of action may occur. The first dose is provided at 28 weeks’ gestation, or after trauma. Singenp.ajorfy of alloimmunization appear to occur at th A second dose is given after delivery of an RhD-positive infant, within 72 hours after delivery. Even if more than 72 hours have elapsed, RhIG should still be given, as it may be effective and is not contraindicated. Other Considerations RhIG is of no benefit once a person has been actively immunized and has formed anti-D. must distinguish women who have been passively immunized by antenatal administration of RhIG from those who have been actively immunized by exposure to Rh-positive RBCs. RhIG is not indicated for the mother if the infant is found to be D-negative. The blood type of fetuses in abortions, stillbirths, and ectopic pregnancies usually cannot be determined; therefore, RhIG should be administered in these circumstances The mother should be D-negative, and the infant should be D-positive or D-variant. Antibody titers are not recommended because the amount of circulating RhiG does not correlate with eftectiveness of the immune suppression or with the amount of fetomaternal hemorrhage. The half-life of IgG is about 25 days, so only about 10% of the antenatal dose will be present at 40 weeks' gestation. It is essential that the anti-D from antenatal RhIG present at delivery not be interpreted erroneously as active rather than passive immunization.  IV The IV product can also be given intramuscu-larly. The intramuscular form must be given intramuscularly only,( IV injections of intramuscular preparations can cause severe anaphylactic reactions because of the anticomplementary activity of these products). RhIG also contains IgA and may be contraindicated in patients with anti-IgA and IgA deficiency who have had anaphylactic reactions to blood products. A maternal sample should be obtained within 1 hour of delivery and screened using a test such as the rosette technique for massive fetomaternal hem-orrhage. If positive, quantitation of the hemorrhage must be done by Kleihauer-Betke or by flow cytometry assays. In the Kleihauer-Betke test, a maternal blood smear is treated with acid and then stained with counterstain. Fetal cells contain fetal hemoglobin (Hgb F), which is resistant to acid and will remain pink. The maternal cells will appear as ghosts After 2000 cells are counted, the % of fetal cells is determined ; Number of fetal cells x Maternal blood volume / Number of maternal cells= Volume of fetomaternal hemorrhage Bec one 300 ug dose covers 30ml of whole volume blood, the calculated volume of fetomaternal hemorrhage is then divided by 30 to determine the number of required vials of RhiG. Because the Kleihauer-Betke is an estimate, one vial is added to the calculated answer. When needed, the additional vials of RhIG should be administered within 72 hours of delivery or as soon as possible. Although it has been a key test as described for many years, the Kleihauer- Betke test is imprecise, and recent attention has focused on newer tech- nologies, such as flow cytometry, to provide more accurate quantitication of the FMH volume. Maternal Weak D In certain patients, serologic reagents do not accurately detect the RhD type. The most common genetic backgrounds that account for this serologic typing problem are called weak D phenotypes. Recently, encouraged the use of RhD genetic testing for patients with a weak D phenotype to provide accurate and actionable results for RhD blood typing and RhiG administration. Anti-D Immunoglobulin Administration in Pregnancy  mm in  DIFFERENTIAL DIAGNOSIS  RBC enzyme disorders, e.g. G6PD and pyruvate kinase deficiency o  Disorders of hemoglobin synthesis e.g. alpha - thalassemias  RBC membrane abnormalities, e.g., hereditary spherocytosis, elliptocytosis. Hemangiomas (Kasabach–Merritt syndrome) mum Acquired conditions, such as sepsis, infections with TORCH or parvovirus B19. add won't  B E Inf  C b A C B a d b c d