3rd Trimester

Blood type changing...Rhogam shot

With my first pregnancy my blood tested as O- and I needed the Rhogam shot.  Baby was A+ so I needed it again after birth.  With this pregnancy (3 years later) my blood is testing O+ (even tested it twice) and my doctor doesn't feel I need the Rhogam shot.  My mom said when I was younger she was once told I had O- blood and once told O+ blood.  I am not sure how this is possible.  Anyone know???  Should I be worried about not getting the shot?

Re: Blood type changing...Rhogam shot

  • Wow, I've never heard of blood type changing... is that even possible?  I'd get the shot just to be on the safe side. 
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  • If the shot is not harmful for rh + people, I would get it just in case.
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  • image LaVieEnRose3411:
    Wow, I've never heard of blood type changing... is that even possible?  I'd get the shot just to be on the safe side. 

    It is very rare, but can change if you'd had a bone marrow transplant or an autoimmune disease.  I'm willing to bet either this new test or the original one was wrong.

  • image Moneypenny424:

    image LaVieEnRose3411:
    Wow, I've never heard of blood type changing... is that even possible?  I'd get the shot just to be on the safe side. 

    It is very rare, but can change if you'd had a bone marrow transplant or an autoimmune disease.  I'm willing to bet either this new test or the original one was wrong.

    This OR already having Rhogam in your system. If you are negative, get the shot, your blood type will test + for the 10 weeks or so.

    Seems strange to me. I'm O - and have been my whole life. If you needed it before, to be safe, I'd ask for it again. If you are +, it can't hurt you, and if you are -, you need it. 

  • I'd be getting a second professional opinion on that one. 
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  • It's very rare, but possible. My aunt also has a blood type that 'switches' from positive to negative and back and in fact before they could synthesize the structures needed to make Rhogam, she donated blood 4x a year because they used it to make the non-synthesized version.

    Most likely though, it's that one test or the other was incorrect. I was previously tested as A+ about a year and a half ago, but when they tested me during my pregnancy, I was A-. Rhogam is not going to cause any problems if you take it and don't need it (other than the momentary pain of the injection).

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  • So I'm not the only one!!! When my OB told me at my very first appointment that I was O- I was like UM...what? We went to my mom & dad's and sure enough, the documents from the day I was born said O+! My OB re-tested me and I am indeed O-, and couldn't say much more than the test done when I was a newborn may have been incorrect. Good to know...you'd think they would be on top of it, lol.

     

    But anyway OP, the Rhogam shot isn't harmful to - or +, so I would ask for it just in case, especially since you had to have it with your first baby.

  • I work where we do testing on blood to determine blood type. Your blood type isn't changing. What is probably happening is you are considered "Weak D" expression of the Rh factor. (the + or - after your lettered blood type). Depending on what lab you get your blood work on, it may or may not be picked up. Hence, one lab says you are Rh negative and now another lab says you are positive. (Or the lab changed methodology of determining Rh and it is more sensitive, so picked up as positive this time). If you had been tested twice (and by this I mean had your blood drawn 2 different times) and you came back as positive, I would not doubt that result. You do not need the Rhogam shot because really you are Rh positive. Hope this helps.

  • image cbiewer:
    I work where we do testing on blood to determine blood type. Your blood type isn't changing. What is probably happening is you are considered "Weak D" expression of the Rh factor. (the + or - after your lettered blood type). Depending on what lab you get your blood work on, it may or may not be picked up. Hence, one lab says you are Rh negative and now another lab says you are positive. (Or the lab changed methodology of determining Rh and it is more sensitive, so picked up as positive this time). If you had been tested twice (and by this I mean had your blood drawn 2 different times) and you came back as positive, I would not doubt that result. You do not need the Rhogam shot because really you are Rh positive. Hope this helps.

    This. I've only seen it a hand full of times and it always throws us off a bit at work. Your doctor should be well aware of the "weak D" possibility and explained this to you a bit better. The OBs at my work were happy to explain it to us nurses.

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  • image cbiewer:
    I work where we do testing on blood to determine blood type. Your blood type isn't changing. What is probably happening is you are considered "Weak D" expression of the Rh factor. (the + or - after your lettered blood type). Depending on what lab you get your blood work on, it may or may not be picked up. Hence, one lab says you are Rh negative and now another lab says you are positive. (Or the lab changed methodology of determining Rh and it is more sensitive, so picked up as positive this time). If you had been tested twice (and by this I mean had your blood drawn 2 different times) and you came back as positive, I would not doubt that result. You do not need the Rhogam shot because really you are Rh positive. Hope this helps.

    This is what I was going to say.... It actually happened to me - I was tested a couple times at the beginning of the pregnancy through an out-of-hospital lab, and my results came back A-. So I went to the hospital for the Rhogam shot at 28 weeks or whatever, but before they gave it to me they did one last blood test, this one through the hospital lab - and it came back A+. The OB explained to me that although it's not all that common, some people have a "weak" RH factor, and only very sensitive tests will pick it up. I'm guessing something similar happened to you.

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  • Just lurking here, but had to chime in.  From my birth records through high school, I've always been told I am O+.  On my blood test for the OB, it came back A-.  Now I have to get the shot too!  I'd never heard of a positive to negative change, much less a type change.  I am guessing something went wrong in a test somewhere, but will get the shot anyway, just to be safe.
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