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Rhogam question

Specializes in Med-Surg, Wound Care.

I have been told by a friend that when she got Rhogam with her first child that future blood typing on her could be altered by the Rhogam. ie. she's obviously negative, but on future typing she could mistakenly be typed as positive due to the Rhogam.

Is this right? I never heard this before and wanted to give her the correct info. I've found nothing in the literature that I've checked.


Specializes in MICU.

I've recieved rhogam 3 times and my blood type is still negative. The rhogam doesn't change the antigens of them mom, it just prevents the development of antibodies to any + blood she may have been exposed to from a baby with a + blood type.

This is my understanding of rhogam; if anyone knows anything different plz share. I'd sure like to know!



lsyorke, RN

Specializes in Med-Surg, Wound Care.

Thanks ICU, that was my understanding too!!! But I haven't worked OB in 20 years... memory ain't what it used to be!!


Specializes in Infection Preventionist/ Occ Health.

ABO group is determined in the laboratory by both forward and back typing, meaning that both the cells and the serum are tested. By contrast, Rh type is determined only by forward typing. Because only the mother's cells are tested, there is virtually no chance of a false positive Rh type due to the presence of Rhogam (anti-D antibodies).

Rh immune globulin (Rhogam) is composed of human IgG directed against the D antigen, and it is routinely given to Rh negative women during the 28th week of pregnancy to prevent development of an immune response. This immune response is caused by fetal-maternal hemorrhage (IgG antibodies can cross the placenta). Common causes of fetal-maternal hemorrhage include abortion (spontaneous or induced), termination of ectopic pregnancy, amniocentesis and childbirth. This immune response only occurs in cases where the fetus is Rho (also called D) positive. Because paternity is not always evident and because roughly 70% of Americans are Rh positive, Rhogam is given to all Rh negative women as a precaution.

HDN (hemolytic disease of the newborn) never affects the first pregnancy, but it may affect all subsequent Rh positive babies of Rh negative mothers if this drug is not administered. Research has found that that Rh negative women with an ABO-incompatible, Rh-positive fetus have a decreased risk of Rh sensitization compared with women with only Rh incompatibility. Though the incidence has decreased dramatically since Rh immune globulin became available, HDN still occurs in cases where the mother does not obtain prenatal care or the amount of fetal red cells entering the bloodstream exceeds the amount of protection provided by the dose of Rhogam. Clinically significant HDN can also occur in rare cases because of ABO group antibodies (IgG only) or other antibodies such as anti-C or anti-K.

Source: Immunohematology: Principles and Practice by Eva D. Quinley

Hope this helps and let me know if you have any questions.

Sable's mom

Specializes in NICU, L&D, OB, Home Health, Management.

Possibly what your friend was supposed to have been told is that anyone receiving rhogam should get a card to carry that gives the date and # of rhogam units they received. For approx 72 hours after rhogam injection it can affect type/crossmatching. This would only matter if something occured in that 72 hours that required a tranfusion.

lsyorke, RN

Specializes in Med-Surg, Wound Care.

I can't thank you enough!!! I'll pass this along.


Specializes in Infection Preventionist/ Occ Health.

The OP specifically asked about the effect on Rh typing. Rhogam DOES NOT have an effect on Rh (D) typing of the mother. The only way this could happen is if there was a SIGNIFICANT fetal-maternal hemorrhage. In this case there might be a mixed field reaction but not a false positive.

It is possible to have a false positive antibody screen for a period of time after receiving Rh immune globulin because both screening cells are Rh positive.


BS Clinical Laboratory Science

Certification: Medical Technologist (American Society for Clinical Pathology)

lsyorke, RN

Specializes in Med-Surg, Wound Care.

Thanks BSN, I'm passing all of this information on.

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