When to administer RhoGAM (Rh immune globulin)?

From the Guidelines

Rh immunoglobulin (RhIg) should be administered to Rh-negative women within 72 hours of spontaneous or induced abortion at less than 12 weeks of gestation, with a recommended dose of 50 mg, or 300 mg if the lower dose is unavailable. This recommendation is based on the most recent and highest quality study, which suggests that a 50 mg dose of RhIg is adequate to cover the volume of potential feto-maternal hemorrhage in the first trimester 1. The study also notes that administration of a lower dose may decrease the concern for resource over-utilization with RhIg administration.

When considering the administration of RhIg, it is essential to prioritize postpartum patients and antenatal patients at later gestational ages for the available doses, especially in situations where the supply of RhIg is limited 1. The American College of Obstetricians and Gynecologists (ACOG) and other authorities have similar recommendations, although they may vary in specific details, such as the dose and timing of administration 1.

Key points to consider when administering RhIg include:

• The dose: 50 mg or 300 mg, depending on availability
• The timing: within 72 hours of potential exposure
• The priority: postpartum patients and antenatal patients at later gestational ages should be prioritized for available doses
• The substitution: an equivalent RhIg product may be substituted if the typically used brand is not available 1.

Overall, the administration of RhIg is crucial in preventing Rh sensitization in Rh-negative women, which can have significant consequences for future pregnancies, including the potential for hemolytic disease of the newborn.

From the FDA Drug Label

For postpartum prophylaxis, administer one syringe of HyperRHO S/D Full Dose (1500 IU; 300 mcg), preferably within 72 hours of delivery For antenatal prophylaxis, one full dose syringe of HyperRHO S/D Full Dose (1500 IU; 300 mcg) is administered at approximately 28 weeks’ gestation. Following threatened abortion at any stage of gestation with continuation of pregnancy, it is recommended that a full dose of HyperRHO S/D Full Dose (1500 IU; 300 mcg) be given. Following miscarriage, abortion, or termination of ectopic pregnancy at or beyond 13 weeks’ gestation, it is recommended that a HyperRHO S/D Full Dose (1500 IU; 300 mcg) be given. If pregnancy is terminated prior to 13 weeks’ gestation, where licensed, a single dose of HyperRHO® S/D Mini-Dose (250 IU; 50mcg) may be used instead of HyperRHO S/D Full Dose (1500 IU; 300 mcg) Following amniocentesis at either 15 to 18 weeks’ gestation or during the third trimester, or following abdominal trauma in the second or third trimester, it is recommended that a HyperRHO S/D Full Dose (1500 IU; 300 mcg) be administered. In any case, a HyperRHO S/D Full Dose should be given within 72 hours after delivery if the baby is Rh positive

Administration Timing:

• Postpartum: within 72 hours of delivery
• Antenatal: approximately 28 weeks’ gestation
• Threatened abortion: at any stage of gestation with continuation of pregnancy
• Miscarriage, abortion, or termination of ectopic pregnancy: at or beyond 13 weeks’ gestation
• Pregnancy termination prior to 13 weeks: where licensed, a single dose of HyperRHO S/D Mini-Dose may be used
• Amniocentesis or abdominal trauma: at either 15 to 18 weeks’ gestation or during the third trimester
• After delivery: within 72 hours if the baby is Rh positive 2

From the Research

Administration of Rhogam

• Rhogam should be given to Rh-negative women in the following situations:
  • After delivery of an Rh-positive infant, within 72 hours of delivery 3
  • At 28 weeks' gestation, when fetal blood type is unknown or known to be Rh-positive 3
  • After miscarriage or threatened abortion, with a minimum dose of 120 microg before 12 weeks' gestation and 300 microg after 12 weeks' gestation 3
  • After ectopic pregnancy, with a minimum dose of 120 microg before 12 weeks' gestation and 300 microg after 12 weeks' gestation 3
  • After molar pregnancy, because of the possibility of partial mole 3
  • After amniocentesis, with a dose of 300 microg 3
  • After chorionic villous sampling, with a minimum dose of 120 microg during the first 12 weeks' gestation, and at a dose of 300 microg after 12 weeks' gestation 3
  • After cordocentesis, with a dose of 300 microg 3
• The dose of Rhogam may vary depending on the situation, with a minimum dose of 50 microg before 20 weeks' gestation and 100 microg after 20 weeks' gestation 4, 5
• If the volume of fetomaternal hemorrhage (FMH) is assessed, a dose of 10 microg of Rhogam per 0.5 mL of fetal red blood cells or 1 mL of whole fetal blood is indicated 4, 5

Timing of Administration

• Rhogam should be administered as soon as possible, but no later than 72 hours after the event 3, 4, 5
• If prevention of RhD alloimmunization is not performed within 72 hours of a potentially sensitizing event, it is still reasonable to administer Rhogam within 13 days, and in special cases, administration is still recommended up to a maximum interval of 28 days postpartum 4, 5

Special Considerations

• Cell-free DNA tests to predict fetal red blood cell antigen genotypes may be used to prioritize the administration of Rhogam to Rh-negative pregnant people in cases of RhIg shortage 6
• The American College of Obstetricians & Gynecologists (ACOG) suggests that utilizing cell-free DNA tests to determine fetal RhD status is a reasonable approach to prioritize RhIg administration when supply is limited 6