How would you identify an Rh incompatibility?

On the first pregnancy of the Rh(-) mother, the fetus will not be affected

On the first pregnancy, the mother still has no contact with Rh(+) blood thus it has not antibodies against Rh(+). After the first pregnancy, even if terminated into an abortion, there is already the possibility of mixing of maternal and fetal blood so this can trigger the maternal blood to produce antibodies against Rh(+) blood. The fetus takes its blood type usually form the father.