Today at the lab ,a very frustrated beautiful young girl entered for walk in laboratory investigation.She wanted to know her blood group and as l prepare to take the sample , l curiously asked for her reason for that test.She told me her boyfriend said some blood do not match with others so he is O positive and if the lady is not O positive it means they can't marry.l nodded and continued with the lab test.l issued the report to her and added "so now that you are A Positive, does it mean you are ending everything with your boyfriend?".
I called her in my office and educated her about such wrong school of thought.l believe she has unlearn and relearn.
I have this feeling that most people out there have same perception that some blood group members can't marry others but today l want to use this hiveghana platform introduced to me by 
Basically there are over 50 blood group systems and the common ones we know of are the ABO and Rhesus system.Under the ABO blood grouping system someone may be A ,B, AB or O depending on the presence of absence of the antigen they inherit and under the Rhesus system the person may be Positive Rh(+) or Negative Rh(-) depending on the presence of absence of the Rh antigen on the RBC.
So if someone inherits antigen A from the ABO system and positive rhessus s/he becomes A Rh(D) Positive commonly know as "A Positive" and if this same person do not inherit the Rh antigen s/he becomes A Rh(D) Negative commonly called "A Negative".
Many people are "O Positive" and this means under the ABO system they did not inherit either A or B hence the "O" and they inherited the Rhesus antigen making them "O Rh(D) Positive".
What make two partners incompatible?
The problem of who you can or cannot marry doesn't come from the ABO system but from the Rhesus as to either you are Positive or Negative.
What happens at the Rhesus level is that anytime a rhesus positive blood Rh(+) is introduced into a Rhesus negative Rh(-) person, the system of the Rhesus negative see the positive blood as a foreigner (attacker) so it mounts antibodies (defends) which destroys all the Rh positive blood .
So let's take Rhesus negative woman and rhesus positive man.
If the woman (Rhesus negative) gets pregnant and unfortunately the baby inherits the Rhesus gene from the father who is positive,the baby is seen as a foreigner and a threat to the mother so the mother's system mount antibodies against the foetus and destroy it causing miscarriage.
This happened mostly after the first pregnancy because for the first time the system is just being sensitized and the antibodies do not attack the baby in the first pregnancy. So the issue is when a Rhesus negative woman trying to conceive with Rhesus positive man.There is a chance that the baby will inherit rhesus positive from the father and there will be miscarriages in subsequence pregnancies.
Why is it not a concern?
There is a medication called Rhogam which is used to prevent Rh immunization in individuals with Rh-negative blood type whose potential husbands are rhesus positive.
It prevents the formation of Rhesus antibodies which can attack the foetus and if it has formed already from any exposure with the Rh positive blood , it neutralizes it.
There's no side effect from this medication hence any blood group can marry the other .
The next time anyone tells you that s/he can't marry you sake of blood group,be bold and eduacte him/her like you have been educated today.
Blood group does not prevent you from marrying anyone.
All women in reproductive age are to know their blood type and prepare ahead for this injection
Dr.Love ,the Lab Scientist 🥼