Little-c antibody with a Rh negative baby

[Antrita]

I have a question. If you have a mother that is Rh positve with an anti-c antibody. The baby is Rh negative with a positive direct coombs. The baby has Anti-c coated cells. Since Rh negative blood is almost 100% little c positive, you would have to transfuse Rh positive blood. How long does it take for an antibody to no longer be detected?

Antrita

[SMW]

The half-life of most IgG is about 23 days so it would be weeks to months before all of the antibody would naturally be gone. If you’re performing exchange transfusions though you will be removing some of the antibody (in addition to the sensitized cells and accumulated bilirubin) so the rate of disappearance will be dependent on the frequency and volume of the exchanges.

Not to question your results, but what method did you use to determine the infant is D-negative? I was also wondering if the positive DAT might be complicating or limiting the D testing? If the infant is indeed D-negative that suggests the mother would have to be an R1/r’ and passed on the r’ gene. Only about 1% of the c-negative individuals are R1/r’ so it is possible, just somewhat unusual. Most c-neg individuals are R1/R1 so would pass on an R1 gene (D-positive). I’ve encountered a similar scenario (anti-c) in a case requiring intra-uterine transfusions and it took a while to convince the Docs we could use D-positive blood for the procedure since it was likely (99+) the infant was D-positive (and this was confirmed after fetal sample obtained at first procedure).

That said though, you have a few choices if the infant needs to be transfused or exchanged.

1. D-negative blood that is c-negative exists. You will need to submit samples to an accredited laboratory that will confirm the testing and then has access to a rare donor program, e.g., the American Rare Donor Program (ARDP). The sooner you submit, the sooner the process can be initiated. Why is it always on a Friday ??

2. You can use D-negative, but c-positive units. You will likely need to perform more frequent exchanges since any circulating passively acquired anti-c will attach to these transfused cells and result in an increased rate of destruction of those cells. Eventually though you will have “mopped-up†all of the passive antibody with the transfused then removed cells and final transfusions will have normal survival. Blood incompatible with the passive antibody is often used for exchange transfusions when compatible blood is “rare†or not immediately available and removing accumulating bilirubin is the critical outcome of the process.

3. You can use c-negative but D-positive units. The units will be compatible with the passive anti-c so less frequent exchanges may be required but you risk sensitizing the infant to the D antigen—but that’s believed to be a rare occurrence with neonates.

Decisions, decisions, decisions..........

[Antrita]

This was just a "what if" question. Our NICU isn't open yet. I am just trying to come up with possible situations that might occur. One time we had a O positive baby come thru the ER. The mother was B positive with an Anti-c. We gave the baby O Positive little-c negative. So, I was just thinking about what we would have done if the baby was Rh negative. Thank you. Hopfully we won't have to worry about this one.

Antrita

[SMW]

Oh. Well then, particularly with the scenario you described, I would suggest when developing your procedures you do not make them so specific that you end up limiting the number of products you have to choose from and therefore on occassion needlessly delay transfusion or create situations where you need to routinely deviate from your SOP (and obtain all appropriate approvals). For example, don't write in your SOPs that you will only use O Negative blood for neonate transfusions. If the neonate is Rh positive, O Positive blood can be used, or better yet ABO specific (if compatible with Mom.). I understand how everyone wants to keep things as simple as possible, but we're working with a limited supply of biological products and sometimes blood bankers actually need to think!........that's why we get paid the big bucks.

[Antrita]

That is good advise. Trying to come up with every "What if this happens?" could lead me to an extremely long NICU procedure manual that no one would read because it is "too long". They will just call me anyway.

Antrita

[YorkshireExile]

This scenario actually happened at our hospital. An R1r` mother gave birth to an O Neg baby with anti-c. We had debates about what to give and decided the best would have been to give R1R1 blood and then consider giving Rhogam. We thought it is best to possibly alloimmunize the baby and have it survive rather than die or get brain damage and not make anti-D. Hopefully it wouldn`t have made anti-D anyway due to immune system immaturity. Fortunately the baby responded well to phototherapy and we managed to avoid a transfusion. Gave us plenty of food for thought though!

[SMW]

Glad to hear the baby did well and you were able to avoid transfusion. Certainly the Rh-positive blood could be an option but to then administer RhIgG seems like it would be counter-productive. You're doing the exchange to remove passively acquired maternal antibody © and sensitized cells (c-positive) that would be destroyed at an increased rate and creating the bilirubin load, but now you're going to administer another passive antibody (D) that will attach to the transfused cells (D-positive), sensitizing the transfused cells, which would then result in the transfused cells being removed at an increased rate and continuing to contribute to the bilirubin load?? The outcome of sensitizing a few cells (15mL) in an adult blood volume vs. sensitizing the entire blood volume in an infant (or even adult for that matter) are very different.

[labgirl153]

Just for fun - see "neonatal quandry" posted in "case studies" on the forum

back in 2007.

[bbbirder]

Always be aware of preganancies involving egg donors.

We had an R1R1 woman make anti-c with her first viable pregnancy from an egg donor. Infant was rr. Fortunately, the titer wasn't very high and the infant didn't require exchange transfusion.

This antibody was a surprise. I am not sure if OB docs consider doing a 2nd antibody screen (as they do on Rh negative females) on pregancies from donor eggs, but it seems like a good idea.

Linda Frederick

[L106]

Always be aware of preganancies involving egg donors.

We had an R1R1 woman make anti-c with her first viable pregnancy from an egg donor. Infant was rr.

Linda Frederick

Linda -

It's good that you brought this up. Artificial insemination is becoming more common, and many of us never think about that possibility when we are evaluating our test results. Thanks for the reminder!

Donna