Hello and welcome to HCM,
The AB + blood group
suggests presence of both AB antigen in and absence of Rh factor
in your blood.
Reactions can occur when there is mis-matched blood transfusion
and a getus with different blood group.
In case the fetus has different blood group, anti D immunoglobulin factor is given within 72 hours of delivery. As you have mentioned you have had the antiserum at the time of delivery.
Mixing of blood (as you have mentioned) does not cause transfusion reaction.
So, there is nothing to worry about the reaction.
However, there is risk of reaction in subsequent pregnancies in which case you have to take anti D immunoglobulin again.
thanks and take care
Dr Shailja P Wahal