Rh factor antibodies
Rh is a red blood cell surface marker. When a mother lacking this marker (rh -) has a pregnancy
with an rh+ infant, she may make antibodies to the babies blood causing the baby to be anemic (low red blood count
This may be very dangerous. To prevent this the mother can be given an injection of rh antibodies to prevent her from making the antibodies that might attack her baby's blood.