Hemolytic Disease of the Fetus and Newborn (HDFN) - Part 2

Hemolytic Disease of the Fetus and Newborn: RhoGAM Overview

RhoGAM (Rh Immune Globulin)

  • Definition: RhoGAM is a solution of concentrated anti-D immunoglobulin, primarily used to prevent Rh immunization in Rh negative individuals.

  • Administration: The standard dose is 300 micrograms, which can be administered either intramuscularly or intravenously.

    • Generally, it is given intramuscularly, often in the buttocks or arm.

  • Source: RhoGAM is prepared from pooled human plasma that has been hyperimmunized and contains the IgG form of anti-D.

  • Indication: It is indicated for pregnant Rh negative women, typically between 28 to 30 weeks gestation, who have not yet developed anti-D antibodies through immunization.

Importance of RhoGAM in Pregnancy

  • Prevention of Sensitization: Rh negative mothers carrying an Rh positive fetus have a 1.5% to 1.9% chance of becoming sensitized, and RhoGAM helps prevent this.

  • Maternal-Fetal Blood Mixing: During delivery or complications of pregnancy, fetal blood may mix with maternal blood, posing a risk of sensitization.

RhoGAM and Antibody Screening

  • RhoGAM administration will result in a positive reaction during antibody screening.

  • On detecting a positive screening, a follow-up identification panel must be conducted to identify anti-D, emphasizing the need to document maternal RhoGAM administration.

  • Reactions to RhoGAM are typically weaker compared to reactions from immune anti-D antibodies developed from sensitization.

Conditions Requiring RhoGAM Administration

  • RhoGAM is beneficial in various situations where fetal and maternal blood may mix:

    1. Invasive procedures: Such as amniocentesis and chorionic villus sampling.

    2. Trauma: Abdominal trauma or accidents.

    3. Delivery of Rh positive infants: Especially with a Rh negative mother.

    4. Transfusions: Mistakenly administering O positive blood to an Rh negative individual can warrant RhoGAM administration.

    5. Ectopic pregnancies or spontaneous/induced abortions.

Specifics on Administration Timing and Dosage

  • RhoGAM should ideally be given soon after delivery of an Rh positive infant, within 72 hours.

  • The half-life of RhoGAM is between 23 to 26 days, necessitating adequate levels until delivery, especially if the gestation exceeds 40 weeks.

  • If the mother becomes sensitized and forms anti-D, RhoGAM is ineffective.

Laboratory Testing for Hemolytic Disease of the Fetus and Newborn

  • After delivery, cord blood is collected for analysis, including:

    • Blood Type: Determines the Rh status of the infant.

    • DAT (Direct Antiglobulin Test): Checks for the presence of maternal IgG antibodies coating the infant's red blood cells.

    • Hemoglobin levels: Assesses for anemia, along with bilirubin levels to check for hyperbilirubinemia.

Management of Hemolytic Disease of the Fetus and Newborn

  • Phototherapy: One of the primary treatment modalities for elevated bilirubin levels and jaundice in newborns. Ultraviolet light converts toxic unconjugated bilirubin into non-toxic isomers.

  • IV Immunoglobulin (IVIG): Helps reduce hemolysis by competing with maternal antibodies for Fc receptors on macrophages.

  • Transfusions: Administering small volume aliqouts from a single unit for treating anemia, especially in premature infants. Exchange transfusions may be considered in severe cases.

Case Studies Summary

  1. Case Study 1:

    • 32-year-old female, A negative with a positive antibody screen indicating anti-D. Since she lacked prenatal care and RhoGAM, she developed Rh hemolytic disease of the newborn due to maternal-fetal blood mixing.

  2. Case Study 2:

    • May is B negative with a negative antibody screen. After delivering an O positive baby with a negative DAT, the next step is to conduct a fetal maternal hemorrhage screen to ascertain RhoGAM adequacy following delivery.