Haemolytic disease of the newborn is a condition in an unborn baby and newborn that can happen if a small amount of your baby’s red blood cells cross the placenta into your bloodstream. This causes your immune system to react by producing antibodies to destroy your baby’s red blood cells. If these antibodies develop, they will not normally affect your first pregnancy. Your immune system, however, has a good memory, and can produce high levels of these antibodies if there is contact with RhD positive blood in a future pregnancy. This may lead to serious complications for your baby, such as severe anaemia, brain damage and even death in some cases. Due to the potential serious effects of haemolytic disease of the newborn, prevention is the key.