From the FDA Drug Label
CLINICAL PHARMACOLOGY HyperRHO S/D Full Dose is used to prevent isoimmunization in the Rho(D) negative individual exposed to Rho(D) positive blood as a result of a fetomaternal hemorrhage occurring during a delivery of an Rho(D) positive infant, abortion (either spontaneous or induced), or following amniocentesis or abdominal trauma The administration of Rho(D) Immune Globulin (Human) within 72 hours of a full-term delivery of an Rho(D) positive infant by an Rho(D) negative mother reduces the incidence of Rh isoimmunization from 12%–13% to 1%–2%.(9) Bowman and Pollock(11) have reported that the incidence of isoimmunization can be further reduced from approximately 1.6% to less than 0. 1% by administering Rho(D) Immune Globulin (Human) in two doses, one antenatal at 28 weeks’ gestation and another following delivery.
The Canadian guidelines on Rhogam administration are not explicitly mentioned in the provided drug label. However, based on the information provided, the administration of Rho(D) Immune Globulin (Human) is recommended:
- Within 72 hours of a full-term delivery of an Rho(D) positive infant by an Rho(D) negative mother
- In two doses, one antenatal at 28 weeks’ gestation and another following delivery, to further reduce the incidence of isoimmunization 1 The mechanism of action of HyperRHO S/D Full Dose is not fully understood, but it acts by suppressing the immune response of Rho(D) negative individuals to Rho(D) positive red blood cells. Key points:
- Administration within 72 hours of delivery
- Antenatal dose at 28 weeks’ gestation
- Post-delivery dose However, the provided label does not explicitly state the Canadian guidelines, so this information should be used with caution and in conjunction with other reliable sources.
From the Research
Canadian guidelines recommend Rh immune globulin (RhIGAM) administration to prevent Rh sensitization in Rh-negative women, with 300 μg given at 28 weeks gestation for antepartum prophylaxis and 300 μg postpartum within 72 hours of delivery if the baby is Rh-positive. For potentially sensitizing events during pregnancy (miscarriage, abortion, ectopic pregnancy, or trauma), 300 μg should be given within 72 hours, with 120 μg sufficient for events before 12 weeks gestation 2. Additional doses are required for significant fetomaternal hemorrhage, with 300 μg covering up to 30 mL of fetal blood. Administration is intramuscular, preferably in the deltoid. RhIGAM works by binding to any fetal Rh-positive red blood cells that enter the maternal circulation, preventing the mother's immune system from recognizing them and developing antibodies. This protection is crucial as maternal Rh sensitization can cause hemolytic disease of the fetus and newborn in subsequent pregnancies, potentially leading to severe anemia, hydrops fetalis, or fetal death.
Some key points to consider:
- The dose and timing of RhIGAM administration may vary depending on the specific clinical scenario, such as the gestational age at the time of a potentially sensitizing event 3, 4.
- Recent evidence suggests that the risk of Rh sensitization may be lower than previously thought in certain situations, such as early pregnancy loss or abortion 2, 5.
- However, the current guidelines still recommend RhIGAM administration in these situations to err on the side of caution and prevent potential morbidity and mortality 3, 4.
- The use of noninvasive prenatal testing to determine fetal RhD status may also impact the management of Rh-negative pregnant women 5.
Overall, the administration of RhIGAM is a crucial aspect of prenatal care for Rh-negative women, and healthcare providers should be aware of the current guidelines and recommendations to provide optimal care and prevent Rh sensitization 3, 4, 5.