HDFN Overview and Pathogenesis
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What primarily causes hemolytic disease of the fetus and newborn (HDFN)?

  • Destruction of fetal RBCs by maternal antibodies (correct)
  • Infection from maternal pathogens
  • Genetic mutations in fetal blood
  • Transformation of maternal T-cells

    • What percentage of maternal alloimmunization cases is attributed to previous pregnancies?

  • 83% (correct)
  • 14%
  • 95%
  • 4%

    • Which antibodies are primarily responsible for the ABO incompatibility in HDFN?

  • IgM antibodies
  • IgA antibodies
  • IgG antibodies (correct)
  • IgE antibodies

    • What was the primary cause of HDFN before the introduction of Rh immune globulin (RhIG)?

    <p>Maternal antibodies against Rh antigen D</p> Signup and view all the answers

    How often do mother and infant present with ABO incompatibility in pregnancies?

    <p>One in every five pregnancies</p> Signup and view all the answers

    What type of antibodies are primarily found in individuals whose RBCs lack corresponding ABO antigens?

    <p>Isohemagglutinins</p> Signup and view all the answers

    What is the main risk factor for maternal RBC alloimmunization?

    <p>Previous pregnancy</p> Signup and view all the answers

    What class of antibodies are primarily responsible for ABO incompatibility but do not effectively cross the placenta?

    <p>IgM antibodies</p> Signup and view all the answers

    What must be determined if the antibody screen is reactive?

    <p>The antibody identity</p> Signup and view all the answers

    Which antibodies can be ignored due to their cold-reactive nature?

    <p>Anti-IHG</p> Signup and view all the answers

    What is the outcome when serum is treated with a sulfhydryl reagent?

    <p>IgM antibodies are destroyed while IgG antibodies remain reactive</p> Signup and view all the answers

    Which class of antibodies can anti-M and anti-N be classified as?

    <p>IgM or IgG or a combination of both</p> Signup and view all the answers

    In the context of Rh D-negative patients, when should antibody screening tests be repeated?

    <p>If transfusion or antibodies are suspected</p> Signup and view all the answers

    Which type of antibodies are considered common in pregnant women but are not known to cause hemolytic disease of the fetus and newborn (HDFN)?

    <p>Lewis system antibodies</p> Signup and view all the answers

    What is the effect of unexpected antibody screening in Rh D-negative patients?

    <p>It may suggest prior exposure to alloantibodies</p> Signup and view all the answers

    What type of tests are typically employed for screening antibodies in prenatal patients?

    <p>Solid phase testing methods</p> Signup and view all the answers

    Which group of mothers is most likely to have a clinically significant ABO hemolytic disease of the fetus and newborn (HDFN)?

    <p>Group O mothers with group A infants</p> Signup and view all the answers

    What is the typical relationship between ABO antigen development and ABO HDFN severity?

    <p>Poor antigen development results in a milder course</p> Signup and view all the answers

    How does maternal alloimmunization occur?

    <p>From exposure to foreign red blood cells</p> Signup and view all the answers

    What factor increases the risk of fetal-maternal hemorrhage (FMH) during pregnancy?

    <p>Physical trauma to the placenta or fetus</p> Signup and view all the answers

    What is the percentage of Rh-negative individuals who typically respond by forming anti-D after being transfused with Rh-positive RBCs?

    <p>85%</p> Signup and view all the answers

    Which of the following statements about group A2 infants is true?

    <p>Their RBCs are serologically similar to A2 adult cells</p> Signup and view all the answers

    What maternal condition is linked to higher production of high-titered IgG ABO antibodies?

    <p>Tetanus toxoid administration</p> Signup and view all the answers

    At what stage of pregnancy is the risk of fetal-maternal hemorrhage highest?

    <p>Third trimester</p> Signup and view all the answers

    What is the primary reason for RhD-negative maternal sensitization causing severe HDFN?

    <p>Prior pregnancy exposure</p> Signup and view all the answers

    How much can the risk of an RhD-negative mother becoming allosensitized be reduced by the appropriate administration of RhIG?

    <p>From 16% to less than 0.1%</p> Signup and view all the answers

    What is the primary mechanism of action of RhIG?

    <p>Interfering with B-cell priming</p> Signup and view all the answers

    When is the first dose of RhIG typically provided to a D-negative mother?

    <p>At 28 weeks' gestation</p> Signup and view all the answers

    What should be done if more than 72 hours have passed after the birth of an RhD-positive infant before administering RhIG?

    <p>RhIG should still be given.</p> Signup and view all the answers

    Why are antibody titers not recommended for determining the effectiveness of RhIG?

    <p>Circulating RhIG does not correlate with immune suppression.</p> Signup and view all the answers

    What must be done to distinguish between a woman who has been passively immunized and one who has been actively immunized?

    <p>Test for the presence of anti-D.</p> Signup and view all the answers

    What is a potential contraindication for administering RhIG?

    <p>If the infant is D-negative</p> Signup and view all the answers

    What is a primary risk associated with the severing of the fetal to maternal circulation at birth?

    <p>Increased risk of hyperbilirubinemia</p> Signup and view all the answers

    What is the significance of a positive direct antiglobulin test (DAT) in newborns?

    <p>Indicates that antibodies are coating the infant's RBCs</p> Signup and view all the answers

    Why can the strength of the DAT reaction be misleading?

    <p>Positive results can occur without clinical signs of hemolysis</p> Signup and view all the answers

    In which scenario is preparing an eluate particularly useful?

    <p>When the cause of HDFN is questionable</p> Signup and view all the answers

    What role does exchange transfusion play in the treatment of hyperbilirubinemia in neonates?

    <p>It reduces the infant's bilirubin levels significantly</p> Signup and view all the answers

    What is one reason why exchange transfusion is rarely needed today?

    <p>Advancements in phototherapy and IVIG use</p> Signup and view all the answers

    Which of the following statements about infants' blood types is accurate?

    <p>ABO antigens may show weak reactions in newborns.</p> Signup and view all the answers

    What complication can arise during RhD typing due to maternal antibodies?

    <p>A false-negative Rh type known as blocked Rh</p> Signup and view all the answers

    Study Notes

    HDFN Overview

    • HDFN is a rare condition that results from the destruction of fetal and newborn RBCs by maternal antibodies.
    • Maternal antibodies can be either naturally occurring ABO antibodies or develop after exposure to foreign RBCs called alloantibodies.
    • Most maternal alloimmunization occurs due to previous pregnancy (83%), while only 4% is due to previous transfusion.
    • Before the advent of Rh immune globulin (RhIG), 95% of HDFN cases were caused by maternal antibodies directed against the Rh antigen D.
    • Recently, ABO incompatibility has become the most frequent cause of HDFN.

    Pathogenesis of HDFN

    • ABO HDFN:
      • ABO antibodies are present in the plasma of individuals lacking the corresponding antigen.
      • ABO antibodies are predominantly IgM class, which cannot efficiently cross the placenta.
      • IgG ABO antibodies can cross the placenta and attach to fetal RBCs.
      • Group O individuals are most likely to form high-titer IgG anti-ABO antibodies.
      • ABO HDFN is primarily limited to A or B infants of group O mothers with potent anti-A, B antibodies.
      • ABO HDFN is often limited to A or B infants of group O mothers.
      • Tetanus toxoid administration and helminth parasite infections during pregnancy have been linked to higher IgG ABO antibody levels and severe HDFN.
      • The mild course of ABO HDFN is associated with the incomplete development of ABO antigens on fetal RBCs.
      • ABO antigens are not fully developed until after the first year of life.

    FMH (Fetal-Maternal Hemorrhage)

    • Maternal alloimmunization occurs from exposure to foreign RBCs through pregnancy, transfusions, or organ transplants.
    • FMH allows spontaneous mixing of fetal and maternal blood during pregnancy.
    • The mixing increases throughout pregnancy, with a higher risk in the third trimester.
    • Physical disturbances during pregnancy (trauma, abortion, etc.) increase the risk of FMH.

    Maternal Factors

    • Individuals' ability to produce antibodies varies based on complex genetic factors.
    • Rh-negative individuals who receive Rh-positive blood have an 85% chance of developing anti-D antibodies.

    Antibody Identification

    • If the antibody screen is reactive, the antibody identity must be determined.
    • Cold reactive IgM antibodies, such as anti-1, anti-IH, and anti-Lea, are generally not significant.
    • Antibodies such as anti-M and anti-N can cause moderate HDFN, although rarely.
    • A sulfhydryl reagent can be used to differentiate between IgG and IgM antibodies.

    Management of the Infant

    • Cord blood testing is important for ABO grouping and RhD typing.
    • DAT (Direct Antiglobulin Test) is the primary serologic test for HDFN.
    • Elution is sometimes necessary to confirm the cause of HDFN.
    • Exchange transfusion is used to replace the neonate's blood and remove bilirubin and maternal antibodies.
    • The selection of blood products for the transfusion requires careful consideration of the infant's blood type and potential antigens.

    Rh Immune Globulin (RhIG)

    • RhIG reduces the risk of alloimmunization in RhD-negative mothers.
    • The mechanism of RhIG is unclear but likely involves interfering with B-cell priming to produce anti-D antibodies.
    • RhIG doses are given at 28 weeks’ gestation or after trauma, and again after delivery of an RhD-positive infant.
    • RhIG offers no benefit if the mother has already formed anti-D antibodies.
    • RhIG is not indicated if the infant is D-negative.
    • RhIG is recommended for abortions, stillbirths, and ectopic pregnancies, even if fetal blood type cannot be determined.
    • Repeated administration of RhIG does not necessarily correlate with effectiveness.
    • RhIG is available in IV and intramuscular forms with specific considerations for administration.
    • RhIG is contraindicated for individuals with anti-IgA or IgA deficiency and a history of anaphylactic reactions to blood products.
    • A maternal sample should be obtained within 1 hour of delivery for screening for massive fetomaternal hemorrhage.

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    Description

    This quiz covers the overview and pathogenesis of Hemolytic Disease of the Fetus and Newborn (HDFN). It delves into the causes and mechanisms of maternal antibody effects on fetal red blood cells, including ABO incompatibility and Rh antigen interactions. Test your knowledge on this rare medical condition!

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