RhoGAM and Coombs

Specialties Ob/Gyn

Published

I'm a nursing student and we just took our OB final this morning. There was a question on the test that I'm confused by and I was hoping someone might be able to explain.

Let me preface by saying that when we covered this material, we ran out of time and so we never had lecture on this and we were told that it wouldn't be on the test. It wasn't on THAT test, but it showed up on the final. I guessed, but looking at the book and the notes, I'm not sure what the right answer is.

The question had to do with when to give RhoGam. Two of the four answers were obviously wrong. The other two were: "if both direct and indirect Coombs tests were positive" and "if both indirect and direct Coombs tests were negative."

I guessed both positive (seemed logical in that we hadn't talked about it and since we were told it wouldn't be on the test, I didn't even read about it!). Afterwords, a classmate of mine who works as a tech in OB said that was right, but when I looked at the Powerpoint for that lecture, it says you give it if they're both negative. The book only mentions it in one sentance and it's unclear.

So, which is it? I've read a lot about Coombs testing online and it seems to me that it would be if they were both positive you'd give the RhoGam, but the Powerpoint specifically days to do it if they're both negative. Can someone tell me which is right and explain why?

I'm hoping that they'll throw the question out since they did say it wouldn't be on the test, but I'd still like to know for myself.

Thanks!

Bryan

Specializes in OBGYN, Neonatal.
Here is all I know about it. A pregnant woman who is Rh negative gets Rhogam during her pregnancy. After birth, if the baby is Rh neg. also, we don't give Rhogam, but if the baby is positive, we do.

Yes I believe this is our practice also.

In refrence to your question : Rho-GAM is a blood product given to,

  • RH(-) moms delivering an RH(+) baby.

A type and antibody test is done on all moms early in pregnancy and if indicated at 28wks she may recieve Rho-GAM. Later on at delivery a blood sample is taken from the infants umbilical cord (this is called cord blood) and the test done with this blood is called a coombs test. If this coombs test is positive and mom is RH(-), Rho-GAM will be given within 72 hours of delivery.

  • Rho-GAM prevents an antibody response in mom and also prevents hemolytic disease of the newborn in the mom's future pregnancy
  • Rho- GAM is given in the deltiod muscle to the mom.

Hope this is helpful.

Specializes in Postpartum, Lactation.

Rh and Coombs are separate and different. The Coombs tests will be part of a rhogam work up for an Rh neg mom after baby's blood type comes back Rh positive.

Also please note that coombs testing done on babies born to all type O mothers is testing for ABO incompatibility and is not related to Rh status and has no bearing on whether or not mom gets rhogam.

Rh isoimmunization is a problem for mom, ABO incompatibility is a problem for baby.

ITA with Jolie. Your PP notes are correct. Rhogam would only be indicated when the coombs are both neg, indicating no isoimunization.

Many women do not receive adequate prenatal care and therefore it cannot be assumed that every Rh negative mother received a dose of Rhogam at 28 weeks.

Specializes in Postpartum, Lactation.
Later on at delivery a blood sample is taken from the infants umbilical cord (this is called cord blood) and the test done with this blood is called a coombs test. If this coombs test is positive and mom is RH(-), Rho-GAM will be given within 72 hours of delivery.

That is not correct. The direct coombs on the cord blood will indicate only ABO incompatibility in the baby. The blood type will indicate the need for rhogam for mom.

The question in the OP is referring to coombs testing on the mother and it's indication for rhogam administration.

Specializes in NICU.

I don't see where a Coombs test would have any bearing on whether or not a mother gets Rhogam or not, as it would be of no help by that point, just as Jolie pointed out.

I've actually been learning a lot about this very thing lately because my little primary at work was born to a mother that didn't get Rhogam after her first miscarriage because she is from another country and for some reason they didn't give it over there. Therefore the mom was already sensitized ..... made for a very sick baby.

Specializes in Postpartum, Lactation.
I don't see where a Coombs test would have any bearing on whether or not a mother gets Rhogam or not, as it would be of no help by that point, just as Jolie pointed out.

It would be pointless to give a mom with a positive direct and indirect Coombs rhogam, as isoimmunization has already occurred. However, rhogam IS indicated when an Rh neg AND coombs negative mom gives birth to an Rh pos baby to protect her FUTURE babies from hemolytic anemia.

Specializes in NICU.
It would be pointless to give a mom with a positive direct and indirect Coombs rhogam, as isoimmunization has already occurred. However, rhogam IS indicated when an Rh neg AND coombs negative mom gives birth to an Rh pos baby to protect her FUTURE babies from hemolytic anemia.

Correct.

Can someone explain what blood type has to do with Rh. I totally understand that if the mother is Rh- and baby is Rh+ then mother needs Rhogam but every once in awhile I read things about Type O blood and I have no idea what blood type has to do with it.

Specializes in Emergency Department.

Are the Rh- mothers getting the Coombs workups in their labs when they are admitted to L&D? Or is this just academic in discussion?

Specializes in L&D.
Can someone explain what blood type has to do with Rh. I totally understand that if the mother is Rh- and baby is Rh+ then mother needs Rhogam but every once in awhile I read things about Type O blood and I have no idea what blood type has to do with it.

Blood type O has no antigen in it to cause a reaction in a recipeint, that is why O is the universal donor. Type A has A antigens and type B has B antigens and type AB has both A and B antigens. That's why type O can only receive blood from an O donor. The antigens in the other 3 types would cause an O recipient to form antibodies that would break down A, B or AB cells.

If a pregnant woman is type O and has a baby that's type A, the inevitable small amount of mixing of blood could cause her to form antibodies against type A blood, so that a subsequent type A baby would have it's blood cells attacked by mom's anti A antibodies. It works the same way Rh does, just against a different part of the blood type. There is nothing like RhoGam for sensitized Type O moms. Fortunately, ABO incompatability is usually not as severe as Rh sensitization. But that is why many docs do a Type and Coombs on babies of Type O moms. Even if the Coombs is negative, showing the baby's blood has not been broken down in utero by mom's antibodies, these babies are more likely to become jundiced and to require billi lights. Just something for you to be aware to be especially alert for in your babies of Type O moms.

Just academically speaking, thanks.

Specializes in Specializes in L/D, newborn, GYN, LTC, Dialysis.

RhoGAM is only effective given in the case whereby a mom is RH neg and baby is RH positive (in the case of live birth) and when it is given within 72 hours of a live birth, , still birth, induced abortion or miscarriage. COOMBS testing is separate and RhoGAM treatment is not treatment for this problem. You are looking for marked jaundice and will be treating that however.

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