Describe HDN and explain why it is important for a couple to know their blood types before having children

HDN is short for hemolytic disease in newborne. It happens when the Rh negative female conceive a baby from Rh positive father. If the fetus is Rh positive and somehow due to breakage of placenta and mixing of blood of mother and fetus mixes then an immune response will be created against the fetus the antibodies will destroy the fetal cells. This will lead to miscarriage.

Thus blood type of couples must be determined before having children so that preventive measures of HDN can be taken.