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

Answered by
Dr. Prakash H Muddegowda
and medically reviewed by iCliniq medical review team.
Published on Aug 09, 2018 and last reviewed on: Jul 26, 2019

Hi doctor,

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

I am in great trouble right now, how could I give clear explanation to my father about this issue. My father told me he knows two couples of same positive blood group who has been married for 10 years without having 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:

  • Do the same blood group create problem? If yes then what basically create problems?
  • Are there any precautions that need to consider for having baby after getting married with same blood group?
  • Are the diseases like thalassemia occurring because of parent's rhesus factors?

One thing to clarify to clarify is that we are two brothers and two sisters and all the six members of my family have same blood group O positive. My elder sister got baby after 8 years and her husband is B positive. And my younger sister, she always gets sick since her antibody of her blood cell might not strong enough to fight disease.

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

Thank you in advance.

Dr. Prakash H Muddegowda

Geriatrics Hematology Pathology


Welcome to icliniq.com. 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 ABO system and 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.

  • You are O blood group with rhesus positive. O positive is one of the commonest and the oldest blood group and is found in more than 50% of the individuals in the world.
  • 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 kid may have genetic defects or you might not have kids at all due to reduced genetic pool. It is not related to blood group.
  • 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 secondary to suppressed immune system can be seen.

If the girl is not a relative then 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 as genetic counseling. Only among close relatives, the immune system behaves dangerously due to 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 same blood group.

Investigations to be done:

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

Regarding follow up:

For further information consult a hematologist online --> https://www.icliniq.com/ask-a-doctor-online/hematologist

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