mild: in mild rhesus disease the fetus and newborn can tolerate the small increase in rate of haemolysis. After the birth may become moderately jaundiced and mildly anaemic.
moderate: if there are higher rates of haemolysis then the levels of unconjugated bilirubin may stay low. This is because the unconjugated bilirubin can pass across the placenta. The fetus can tolerate the moderate level of anaemia associated with mild rhesus disease. After birth the levels of bilirubin rise rapidly.
severe: in this condition the fetus is not able to maintain haemoglobin and becomes severely anaemic. This condition is associated with a severe disturbance of foetal metabolism and is associated with hydrops foetalis. There may be hypoglycaemia.