This week, a client asked me to answer this question.
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“Hello doctor. My wife and I are blood group A positive (A+) each. Our son is blood group O. Is this possible, or is there a chance that he is not my son?”
The answer to this question is that there is no cause for alarm, because it is perfectly normal and possible for parents who both are blood group A plus to give birth to a child who is blood group O.
The ABO blood grouping system has four main groups: O, A, B and AB, which together with the Rhesus system combine to define the following blood groups: O-, O+, A-, A+, B-, B+, AB- and AB+.
The four ABO blood groups arise from inheriting one or more of the alternative forms of this gene (or alleles) namely A, B or O. The table below shows the possible blood group outcomes for a child, based on the father and mother’s blood group.
It is interesting to note that when both parents are blood group O, then the children can ONLY be blood group O.
However, when both parents are either blood group A or blood group B, then it is possible for the child to be group O. However, if any of the parents is blood group AB, then there is NO possibility of the child having a child with blood group O, even if the other parent is O.