Anonymous
Post 01/25/2026 10:53     Subject: Blood type changed during pregnancy
When I was pregnant, the doctor inputted the incorrect blood type. I pointed it out and she switched it back to O+. She also gave me the wrong meds right before delivery. I was very high risk and it could have gone badly.

She was useless.

Unfortunately I think most doctors are useless.
Anonymous
Post 01/25/2026 10:41     Subject: Blood type changed during pregnancy
Anonymous wrote:
Anonymous wrote:
Anonymous wrote:I had the exact opposite happen sometime between when my third child was born and my fourth child was conceived. I doubt pregnancy had anything to do with it though. Mine changed from type A to type B. It’s technically supposed to be impossible but I have had so much bloodwork done in my life that I have the documentation to prove it. You can see the point in time where it changed from A to B. I have shown medical professionals the documentation. None of them have been able to explain it.


Even if this is true, it is very rare and could be an indication of a serious issue like blood cancer, and would have to be closely monitored and discussed prior to a medical procedure or event where you might need a transfusion … such as delivering a baby. And of course the more likely reason is medical error which needs to be addressed ASAP.


Yes, there are very few explanations for a change in blood type:

One of them is leukemia. if this happened to you years ago, I'm assuming you don't have that, but there's an outside chance OP could have it.

The other is bone marrow transplants (which can change your blood type permanently) or a recent, massive transfusion (which only changes your blood type temporarily).

Other explanations is that you and OP were actually born with a rare variant in which you react to both A and B antibodies, but depending on the test, you may "appear" as either A or B.

Or that you are a chimera, which means that in the womb, you absorbed a twin fetus, or exchanged cells with a twin via placenta, which means you can have two sets of blood types.

It's all worth exploring, because your life could be at risk.


Yes, it's much more likely that there was a mistake but a doctor should not be brushing this off. Retest is a very basic step.
Anonymous
Post 01/25/2026 10:41     Subject: Blood type changed during pregnancy
At my OB/GYN practice, I found out from a confused receptionist that there was a patient with the same last name and same first name (spelling variant though) as me. I had had a few strange "mistaken identity" moments in my town before, and so after that I used LinkedIn to track down my doppelganger. Got in touch and had a pleasant lunch with her (we were both graduates of the same grad program). I wanted to make sure that we knew each other so we could avoid any odd mixup consequences. We had lots of identical resume characteristics and, based on genealogy, her family and mine had branched off from each other about 200 years before. So she actually was a very distant cousin.
Anonymous
Post 01/25/2026 10:34     Subject: Blood type changed during pregnancy
Anonymous wrote:
Anonymous wrote:I had the exact opposite happen sometime between when my third child was born and my fourth child was conceived. I doubt pregnancy had anything to do with it though. Mine changed from type A to type B. It’s technically supposed to be impossible but I have had so much bloodwork done in my life that I have the documentation to prove it. You can see the point in time where it changed from A to B. I have shown medical professionals the documentation. None of them have been able to explain it.


Even if this is true, it is very rare and could be an indication of a serious issue like blood cancer, and would have to be closely monitored and discussed prior to a medical procedure or event where you might need a transfusion … such as delivering a baby. And of course the more likely reason is medical error which needs to be addressed ASAP.


Yes, there are very few explanations for a change in blood type:

One of them is leukemia. if this happened to you years ago, I'm assuming you don't have that, but there's an outside chance OP could have it.

The other is bone marrow transplants (which can change your blood type permanently) or a recent, massive transfusion (which only changes your blood type temporarily).

Other explanations is that you and OP were actually born with a rare variant in which you react to both A and B antibodies, but depending on the test, you may "appear" as either A or B.

Or that you are a chimera, which means that in the womb, you absorbed a twin fetus, or exchanged cells with a twin via placenta, which means you can have two sets of blood types.

It's all worth exploring, because your life could be at risk.
Anonymous
Post 01/25/2026 10:29     Subject: Blood type changed during pregnancy
Apparently blood group A can change to or mimic blood group B in rare cases (see link below), but I don’t see anything about it ever happening the other way around. It may be a typo, or your results may have gotten switched with someone else’s. Trust me when I say human error is everywhere.

https://ourbloodinstitute.org/blood-matters/blood-type-change/
Anonymous
Post 01/25/2026 10:20     Subject: Blood type changed during pregnancy
Anonymous wrote:I had the exact opposite happen sometime between when my third child was born and my fourth child was conceived. I doubt pregnancy had anything to do with it though. Mine changed from type A to type B. It’s technically supposed to be impossible but I have had so much bloodwork done in my life that I have the documentation to prove it. You can see the point in time where it changed from A to B. I have shown medical professionals the documentation. None of them have been able to explain it.


Even if this is true, it is very rare and could be an indication of a serious issue like blood cancer, and would have to be closely monitored and discussed prior to a medical procedure or event where you might need a transfusion … such as delivering a baby. And of course the more likely reason is medical error which needs to be addressed ASAP.
Anonymous
Post 01/25/2026 10:16     Subject: Blood type changed during pregnancy
Anonymous wrote:Given OP'S donor history and parents, it seems pretty obvious the A- test was an error. All those previous data points versus a single test? The outlier has to be the mistake. The doctor didn't perform the test, the lab could have entered or read it wrong or mixed up samples. So the doctor being confident doesn't mean much to me.

You can buy a basic blood typing kit online if you really want.


The doctor not listening and being “confident” is a very bad sign! Blood transfusions are not unheard of in delivery and this could kill OP. Also the blood test that was mixed up would have failed to test whatever was needed now - I’m assuming it was blood glucose.

OP needs to insist the doctor re-order the blood draw and the doctor needs to accept the possibility of an error. If the doctor won’t then it is time for a new doctor. The problem isn’t so much the error (which happens) but refusal to admit to it and fix it in a timely manner.
Anonymous
Post 01/25/2026 10:15     Subject: Blood type changed during pregnancy
I had the exact opposite happen sometime between when my third child was born and my fourth child was conceived. I doubt pregnancy had anything to do with it though. Mine changed from type A to type B. It’s technically supposed to be impossible but I have had so much bloodwork done in my life that I have the documentation to prove it. You can see the point in time where it changed from A to B. I have shown medical professionals the documentation. None of them have been able to explain it.
Anonymous
Post 01/25/2026 10:14     Subject: Blood type changed during pregnancy
This happened with me, and they put someone else’s electronic records in mine. Same name with one letter difference. Very different birthdays, which is how I discovered it.
Anonymous
Post 01/25/2026 10:11     Subject: Blood type changed during pregnancy
They made a mistake. Have them redo the blood draw. If they give you any grief about admitting the mistake, I would change practices.
Anonymous
Post 01/25/2026 10:09     Subject: Blood type changed during pregnancy
Given OP'S donor history and parents, it seems pretty obvious the A- test was an error. All those previous data points versus a single test? The outlier has to be the mistake. The doctor didn't perform the test, the lab could have entered or read it wrong or mixed up samples. So the doctor being confident doesn't mean much to me.

You can buy a basic blood typing kit online if you really want.
Anonymous
Post 01/25/2026 10:01     Subject: Blood type changed during pregnancy
^ you need to ask for a resolution of the ABO type discrepancy. You could even ask for genotyping.
Anonymous
Post 01/25/2026 10:00     Subject: Blood type changed during pregnancy
Wow. OK.

The most likely explanation is that one of the blood types is a mistake (maybe your parents made a mistake in identifying their blood type too).

In very rare cases, people can have chimerism or atypical ABO variants, in which case it should be noted on your donor card and medical chart.

Right now for transfusion purposes, you should be considered O-.

You absolutely need retyping, and they need to do forward and reverse typing, not just the regular basic test. You need to insist, since the OB apparently doesn't believe you.

Do not give blood until you know what you are, and flag this if possible if you need to receive a transfusion in the future.

Fascinating. If you ever get this resolved, I'd love to know, OP.

Anonymous
Post 01/25/2026 09:49     Subject: Blood type changed during pregnancy
That's not possible. Someone made a mistake.
Anonymous
Post 01/25/2026 09:48     Subject: Blood type changed during pregnancy
I’m just wondering if anyone else has experienced something similar. I’m pregnant. Before pregnancy, my blood type was B-. I know this for certain because I have been a blood donor for years, and it says B- on my blood donor card and Red Cross app. When I had my blood drawn recently, I was told that I’m A-. My parents (also donors) are type B and type O, so it’s also genetically impossible for me to be type A. My doctor has told me that it’s not possible for your blood type to change if you have never had a blood transfusion or bone marrow transplant. She seemed sure that I’m A-.

It doesn’t really matter in the grand scheme of things, but my curiosity has been peaked. I wonder if pregnancy can cause something like this and if it will be temporary or permanent.