Q: My wife is pregnant. As per the doctor's advice, we got her blood tested. Her blood group emerged as A positive in 2 different labs. Prior to this her blood group was O positive. Even during her birth it was this. We are unable to comprehend how her blood group can change. Could you please explain if this is possible and would there be any complications due to this?

A:The main blood groups of the ABO blood group system are A, B, O and AB and each of these have various subgroups. More of these are being found as techniques and equipment available for testing improve and some have been found only with the advent of molecular and genetic analysis. The A blood type has the most variation in subgroup of any of the ABO blood types with about 20 different known subgroups. A1 and A2 individuals make up the vast majority of people with A blood type, all other subgroups equal less than 1% of As. The failure to detect a weak subgroup of A may result in a patient or donor being mistyped as group AB or B or O. There is one sub-group called Ax (Ao) which is rare (1/40,000). The main distinguishing features of Ax cells are that the A antigen is so weak it may only be detectable by using anti-A,B and the individual has anti-A1 antibodies present in the serum. If anti-A, B is not used, Ao cells may be mistyped as group O. You can discuss this with the Department of Transfusion Medicine where your wife has recently been tested and the doctor there would be able to explain to you what testing technique was used.