Preventing Rh Alloimmunization
By: O.J. Bradshaw, MLS (ASCP), Laboratory Specialist
OJ Bradshaw, MLS (ASCP), brings 36 years of experience to his role as a laboratory specialist in ACHC's Clinical Laboratory Accreditation Program. Prior to joining ACHC in 2024, he served as a lead medical technologist at his local medical center and later focused on blood bank and microbiology.
Posted: September 16, 2026
Clinical laboratories play an important role in preventing Rh alloimmunization during pregnancy and following obstetric events. It is important to identify Rh immune globulin (RhIG) candidates and ensure appropriate testing occurs.
What is RhIG?
Rh immune globulin (RhIG), also called anti-D, is a blood-derived medication made from human plasma that contains antibodies against the Rh(D) antigen found on red blood cells. RhIG is a preventative treatment given via injection to provide temporary antibodies that prevent the body from producing its own harmful anti-D antibodies.
Who is a candidate?
Rh-negative women may be given RhIG at 28 weeks during their pregnancy as a preventive measure.
Rh-negative women should receive RhIG when there is a risk of fetal-maternal blood mixing, including:
- After delivery of an Rh-positive infant (newborn's Rh status, including identification of weak D phenotype newborns).
- Following a miscarriage.
- Following an abortion.
- After an invasive obstetric procedure (for example, amniocentesis or chorionic villus sampling).
- After abdominal trauma during pregnancy.
Fetomaternal hemorrhage testing
Testing for fetomaternal hemorrhage (FMH) is required to determine the appropriate dose of RhIG. Policy and procedure should identify how this is achieved, whether the testing is sent to a reference lab or done in-house. A fetal screen (rosette test), Kleihauer-Betke (KB) test, and flow cytometry are all commonly used to detect and/or quantify fetomaternal hemorrhage (FMH).
The operating procedure should include a standardized dosage calculation based on the measured volume of fetal red blood cells present in the maternal circulation. There are several brands of RhIG available today. Always follow your manufacturer’s dosage instructions.
Administration
The appropriate dose of RhIG should be administered within 72 hours of delivery or incident to reduce the risk of alloimmunization.
Typically, doses are given via intramuscular or intravenous injection.
Regardless of where RhIG is dispensed or administered, manufacturer guidelines must be followed, including any recommended patient testing and screening requirements.
CMS guidance
The recent CMS QSO-26-07 Hospitals/CAHs memo related to Conditions of Participation for obstetric services requires facilities to have a process to administer this life-saving medication.
--
Read more articles about Clinical Laboratory Accreditation here.