Hello welcome to health care magic sir, Incompatibility in the newborn fetus may cause HDNB(hemolytic disease of new born)depending upon the severity of red cell breakdown..this is because of Rh antibodies developed in the mother(if mother is Rh -ve) because of either previous blood tansfusion or birth to a baby who is Rh+ve.. 1.If the above said antibodies develop before the 1st child birth(that means if blood transfusion done).,,then 1st baby will affect.. 2.If the above said antibodies develop after the birth of 1st child birth your 1 st baby will be normal..and for second pregnancy these antibodies travel across placenta and make red cell to break in the baby.. Rh means rhesus factor...Rh +ve means presence of Rh antigen in the blood..ne negative means absent.. Regarding your query..you are O+ve and your would be is O-ve..If she had prior blood transfusion that too receives +ve blood..then you need to take anti D injection..now a days that +ve blood is not giving to -ve one in the fear of future problems.. After the 1st pregnancy your wife had to receive anti D immunoglobulin to supress her immune status because of baby s blood..after taking of this anti D then further pregnancies would be normal..no problem will arise.. Incompatibility doesn t cause thalassemia,,it is an inborn genetic error in the red blood cells.. There is no side effects to that injection. Before marriage checking for HIV status is mandatory,,..other else not necesssary and not required.. hope you understand my answer and suggestion.. Thank you Dr.siddartha