An Rh-negative mother who was exposed to her fetus's Rh-positive blood during a previous pregnancy or delivery or who has accidentally received an Rh-positive blood transfusion has antibodies against Rh-positive blood cells.
Rh incompatibility may develop when a woman with Rh-negative blood becomes pregnant by a man with Rh-positive blood and conceives a fetus with Rh-positive blood.
If the father is Rh-positive, an antibody screen is done to determine whether the Rh-negative woman is sensitized to the Rh antigen (developed isoimmunity).
A person with at least one copy of the gene for the Rh factor has Rh-positive blood; if no copies are inherited, the person's blood type is Rh-negative.
Conversely, a woman sensitized by previous Rh-positive fetuses may have a high antibody titer during her pregnancy while the fetus is Rh-negative.
This destroys any Rh-positive fetal blood cells in the mother's circulation before her immune system can produce antibodies against them.
If an Rh-negative woman gives birth to an Rh-positive baby, she is given an injection of Rhogam within 72 hours of the birth.
If you are Rh-negative and your partner is Rh-positive, you may need treatment to protect your baby from a blood problem.
These antibodies can circulate in her Rh-positive newborn, initiating hemolysis and causing severe abnormal jaundice.
If she is Rhnegative, the father's blood is tested to determine whether he is Rh-positive.