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Dr. Andrew Rynne

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If both parents have same blood group what will be the child's blood group?

Answered by
Dr. Kalpana Pathak


Practicing since :2006

Answered : 2015 Questions

Posted on Mon, 4 Feb 2013 in Genetics
Question: if both parents have type o neg. blood, and their first two children have o neg. blood, could a third child have o positive? what are the odds? one step futher, what type would a fourth child have?
Answered by Dr. Kalpana Pathak 2 hours later

Thanks for writing to us.

Blood group is always genetically determined.

If both the parents are actually 'O-negative', all the children will be 'O-negative'.

Having said this, O negative parents can only deliver O positive child only if tests were "inaccurate".
Or if the father had weak rhesus D gene that is actually father is positive but tested negative due to weak Rh D gene. In these cases retesting should be done to rule out weaker reaction.

Hope that answers your query. Should there be further questions, I would be happy to assist you.


Above answer was peer-reviewed by : Dr. Prasad
Follow up: Dr. Kalpana Pathak 10 hours later
if the father ha a weak rhesus D gene and the father a actually a positive, even though tested negative would the RH factor exisist for the childredn? espially for a second birth? (I know it as having a blue baby)
Answered by Dr. Kalpana Pathak 1 hour later

Thanks for writing back.

If father has weak rhesus D gene that might pass to the offspring.
However for all practical purposes if both the parents are O negative, all the off XXXXXXX or children have to be O negative, provided the blood tests have been accurately done.

As a general rule, all rhesus negative persons should be tested for weak rhesus D gene as a person with weak rhesus D gene is actually rhesus factor positive.

Hope that answers your query.

Take care
Above answer was peer-reviewed by : Dr. Prasad

The User accepted the expert's answer

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