My blood type is o positive. my son is ab. what is my husband's blood type?

Cannot tell: If a mom has o+ blood type, and says her son is ab (meaning either ab+ or ab negative), there is not enough information to tell what blood type the mom's husband has.

Could be cis-AB: The cis-ab phenotype can raise questions about an apparently paradoxical inheritance of the ABO blood group, such as the birth of an o child from an ab mother. The blood bank can be of assistance to a clinician faced with a patient with what appears to be a genetically impossible ABO blood group. For more details read http://www.Ncbi.Nlm.Nih.Gov/pmc/articles/pmc1686052/ also: http://www.Sciencedir.

See below: You may want to check your blood type again. According to genetics no matter what your husbands blood type is it is impossible for you to have an ab child if you have type o blood.

Cannot determine: You probably are not a true "O" but have transmitted a weak A or weak B to Junior.