Rh Negative

Rh Negative

Each person’s blood is one of four major types (A, B, AB, or O), that is determined by the something called an antigen on the blood cells. Antigens are proteins on the surface of blood cells that can cause a response from the immune system. There are hundreds of different antigens on a blood cell. The Rh factor is a type of protein on the surface of red blood cells.

As part of your prenatal care, you will have blood tests to find out your blood type. If your blood lacks the Rh antigen, it is called Rh-negative. If it has the antigen, it is called Rh-positive. 85% of people are Rh positive and 15% are Rh negative.

If you are Rh-negative, you may develop antibodies to a baby that is Rh-positive. If even a small amount of the baby’s blood mixes with your blood, your body may respond as if it were allergic to the baby. This response causes you to have antibodies to the Rh antigens in the baby’s blood. This is called sensitization and your antibodies can cross the placenta and attach to your baby’s blood cells. They then break down the fetus’s red blood cells and can cause anemia. Antibody screen is another blood test that can show if an Rh-negative woman has developed antibodies to Rh-positive blood.  An injection of a blood product called Rh immunoglobulin (RhIg), can prevent sensitization of an Rh-negative mother.

If a woman with Rh-negative blood has not been sensitized, her doctor will recommend that she receive RhIg around the 28th week of pregnancy to prevent sensitization for the rest of pregnancy.  If the baby is born with Rh-positive blood, the mother should be given another dose of RhIg within 72 hours of delivery to prevent her from making antibodies to the Rh-positive cells she may have received from their baby during delivery. Each pregnancy and delivery of an Rh-positive child requires repeat doses of RhIg.  Rh-negative women should also receive tRhIg after any miscarriage, ectopic pregnancy, or induced abortion to prevent development of antibodies that would attack a future Rh-positive baby.

For further information or to schedule an appointment, please call our Maternal Fetal Care Center at (414) 805-6624.