Rh factor is an inherited protein found on red blood cells. A person whose blood has this protein is Rh positive, and if the blood lacks the protein is Rh negative, according to WebMD.
Rh blood types are crucial in women. Having either type of blood has no adverse effects on the health of a person. However, problems occur if a woman with a negative Rh blood type becomes pregnant with a baby whose blood type is Rh positive. If the blood of the mother mixes with that of the fetus during the pregnancy or delivery, the mothers immune system detects the babys blood as antigens and reacts by producing antibodies. This action can damage the babys red blood cells, states WebMD.
The antibodies produced by the mother have no effects on the baby during the first pregnancy. Problems occur if the woman gets pregnant again with an Rh-positive baby. This can result in delivering a baby with anemia, a condition characterized by a deficiency of red blood cells, says Mayo Clinic.
A blood test is necessary for pregnant women to check on their Rh factor. If a woman has a negative Rh blood type, the doctor may recommend a shot of Rh immunoglobulin, which prevents the production of antibodies against the babys antigens, notes WebMD.