Q. Me and my fiance have same blood group. Will it affect our baby?

Answered by
Dr. Prakash H. M
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Aug 09, 2018 and last reviewed on: Jun 01, 2023

Hi doctor,

I am 30 years old. I am planning to get married to a girl who is known to me. We have a very good understanding. But, we have the same blood group that is O-positive. Since the blood group is a factor in having babies, do you think having the same positive blood group could create problems for future generations? My father is very concerned about this. He talked with several doctors and they ensured that it could create problems. And they do not want me to marry this girl. I spoke with another doctor and she replied that it is not a big problem.

I am in great trouble right now, how could I give a clear explanation to my father about this issue? My father told me he knows couples of the same positive blood group who have been married for 10 years without having a baby. And doctors could not find any problems for both men and women. But their blood immune system did not match to have a baby.

I have these questions:

  1. Does the same blood group create problems? If yes then what basically creates problems?
  2. Are there any precautions that need to consider for having a baby after getting married to the same blood group?
  3. Are the diseases like thalassemia occurring because of parent's rhesus factors?

One thing to clarify is that we are two brothers and two sisters and all the six members of my family have the same blood group O positive. My elder sister got a baby after eight years and her husband is B positive. And my younger sister always gets sick since the antibody of her blood cell might not be strong enough to fight disease.

My father explained, due to my parents having the same blood group; my sisters might get those above-explained problems. I will explain my family based on your explanation.

Thank you in advance.



Welcome to Based on your query, my opinion is as follows:

There are two major blood group systems and more than 400 minor blood group systems.

The major blood group systems are the ABO system and the Rhesus system, which are important. In the ABO system, there is A, B, AB, and O. While in Rhesus, if it is present, it is positive, and if not then negative.

  1. You are O blood group with a rhesus positive. O positive is one of the commonest and oldest blood groups and is found in more than 50% of the individuals in the world.
  2. When the female is O negative and the male is O positive, there is a future risk for the fetus with a condition called hemolytic disease of the newborn. If both are O positive then there is no risk.
  3. Now regarding the girl known to you, if she is a close relative (second or third-degree relative) then the marriage can create a reduced genetic pool. Hence, future kids may have genetic defects or you might not have kids at all due to a reduced genetic pool. It is not related to the blood group.
  4. There are so many common genes amongst relatives and some are suppressed. So, when they get married, these suppressed may get activated, and genetic abnormalities or diseases which are secondary to suppressed immune systems can be seen.
  5. If the girl is not a relative then the blood group is hardly a concern. If both are O positive, it would not matter.

If she is a relative, get genetic tests to rule out any common diseases, which can affect the future kid. This test is called genetic counseling. Only among close relatives, the immune system behaves dangerously due to a reduced genetic pool.

To conclude, having a common blood group is not a problem. She can donate blood to you and you to her in emergencies just like your siblings can. No other complications with the same blood group.

Investigations to be done:

If necessary in case of second or third-degree​ relative then genetic counselling

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