Me and my wife's blood type is AB+, she is now at week 13 and blood test showed antibodies. She had a miscarriage before. Should we be worried?

Not for Rh antibody. You did not indicate which antibodies your wife has, but she should not have any Rh antibodies, if she is truly AB+ (the + indicates the presence of the Rh antigen). Since she has Rh antigen, she should not develop antibodies to this antigen. However, there is the possibility that she could have other antibodies if she was exposed either through previous pregnancy or transfusions.