Weak D Blood Type and Pregnancy
DISCLAIMER: I am not a medical professional and information I present here is from research that I have done and my personal experiences. You should always consult a medical doctor with any of your healthcare questions.
So you’ve been told that your blood type is “weak D” or maybe you know someone who has been told that they are “weak D.” Now what? What does it mean for you and your pregnancy? How is it supposed to be treated?
First let me give you a little background to what being “weak D” actually means. During pregnancy, it is standard protocol to get your blood typed to determine if you are RH positive or RH negative. The reason it is important to do this is because if your body produces RH negative blood and your baby’s blood type is RH positive, your body can develop antibodies. These antibodies could potentially affect any following pregnancies if you are carrying a baby with a positive blood type. In other words, your body could see the baby’s blood as “foreign” and attack it. No one wants that to happen, so that is why blood typing occurs during pregnancy.
In order for your blood to be classified as RH positive or RH negative, labs will look for the D antigen in the blood. If there is an adequate amount of the D antigen on the blood cells and a reaction is seen when mixed with anti-D, then that blood type is classified as RH positive. If the D antigen is not seen on the blood cells and no reaction is seen when mixed with anti-D, then you would be classified as RH negative. Current treatment for RH negative women in pregnancy, is to receive the Rhogam shot at 28 weeks and following the birth of the baby. The Rhogam shot consists of pooled blood of RHo (D) immune globulin that is used to prevent the body from creating an immune response to RH positive blood.
So what about the “weak D?” If a persons blood type comes back as RH negative, some labs may take a step further to determine if the D antigen is present at all and if ANY reaction is seen with anti-D. Approximately .2%-1% of Caucasians have the weakly expressed D antigen. Historically, the “weak D” blood type will have some reaction with some anti-D but not with others. The D antigen is “weakly present” meaning that there is less of the D antigen per blood cell than that of a normal RH positive person. If the lab does not take this extra step, then the blood work would come back as RH negative.
I have the perfect example of this… me.
During my first pregnancy, I went to my 24 week appointment and was told that I needed the Rhogam shot. The doctor I was seeing for that appointment did not give me any background information for me to understand why the Rhogam shot was needed or even what it was. After I pressed for more, I found out that my blood type was “weak D” and the current treatment for those with “weak D” was to get the Rhogam shot at my 28 week appointment.
So, of course, I went home and did A TON of research because I wanted to make sure I was making an informed decision before getting an injection that could be unnecessary. The conclusion that I came to was that there was no consensus on how to treat patients with the “weak D” blood type. I found some practices that felt it was better to be safe and therefore treated those with the “weak D” as RH negative, and I found some practices and articles that stated the “weak D” was still a positive blood type and the Rhogam shot was not necessary for these patients. This was very frustrating for my type A personality as I like for things to be black and white. This was definitely a GRAY situation!
I went back for my 28 week appointment, seeing a different doctor, and I expressed my concern to her. She proceeded to tell me that she had called the lab and since my blood type was “weak D positive” that the Rhogam shot was not needed. So that was the decision I went with in my first pregnancy.
{This is the frustrating thing about seeing multiple doctors within a practice. They all have their own standards and beliefs for which they abide by on how to treat a patient.}
Now fast forward to the present.
I am now 28 weeks pregnant with my second pregnancy. At my 24 week appointment, the doctor came in (a different doctor than before), and said “so we need to talk about your blood type.” Now that I have experience in this area, I new where the topic was going. She told me that the current standard is to have the Rhogam shot for the “weak D” blood type. I told her that I didn’t understand why, since I did not need it in the first pregnancy. She said it was the new standard. So, naturally, this was frustrating for me. Ultimately, she said, it was up to me to make the decision to get the shot, she just wanted to give me the information to make an informed decision. (I did ask if my body had developed antibodies against the positive blood type since my daughter was born with B+ blood, and the doctor told me I had not.)
Here are a few facts the doctor told me.
If a person is completely RH negative, and they decide not to get the Rhogam shot, their chances of developing antibodies against the D antigen is 17%.
If you get the Rhogam shot, it reduces the risk to less that 1%.
Naturally, I was very frustrated again, because I thought I had this figured out from my previous pregnancy, so again, I went home and did A TON of research.
Here is what I found:
The AABB Advancing Transfusion and Cellular Therapies Worldwide came out with a Joint Statement regarding how pregnant women with “weak D” should be treatment. In this statement, they stated that 80% of persons with the “weak D” expression are weak D type 1, 2, or 3 when additional testing of RH genotyping is performed. Women who are child bearing with any of these types can be managed as RH positive and the Rhogam shot is not needed. In other words, I needed to find out what “type D” I was so that I could make an informed decision on whether or not the Rhogam shot was needed.
It took A LOT of research but I found the black and white I had been looking for!
I did further research and found a lecture that further explained “weak D” and also gave a CPT code for billing purposes for the RH genotyping. If you are someone who wants to have your “weak D” typed, then you will need the CPT code 81403. When I found this, I called my health insurance and made sure it was a covered service.
When I went to my 26 week appointment, I made my case. I told the doctor (also a different doctor) that I wanted to have my “weak D” typed and gave them the CPT code. Come to find out, the lab that was being used this go-around, did not take my blood typing a step further and so my blood type came back as RH negative. This means, I never would have known that I was actually “weak D!” The doctor I saw was very understanding and APPRECIATED MY RESEARCH!! She actually THANKED ME!! I’m sure they don’t see very many patients with this blood type and I’m sure it is very hard to be up to date on everything, so for me to bring this information to the practice, was appreciated. I was so happy!
My blood test came back and I am Weak D Type 1. No Rhogam shot for me.
I hope this article was beneficial for you to read and that you find the resources useful! I know that I have given myself the best medical care that I could have and now know for any future pregnancies that I do not need the Rhogam shot.
Good luck in your pregnancy journey!
Love y’all!
“Happy Home Sweet Home”
Brittany
Some additional resources for you!
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320789/
https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0015068/
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