Each of us falls into one of four blood types: A, B, AB, or O. All of these blood types can either have a certain protein (called an antigen) on the surface of the red blood cells or not. If you do have this protein on your blood cells, you’re considered Rh-positive. If you do not have these proteins, you’re considered Rh-negative.
Why is this important? Because if you’re Rh-negative, and your partner is Rh-positive, there’s a good chance your baby will now be Rh-positive, too. And that can become a problem, because your blood may start to make certain antibodies that attack those fetal blood cells. In other words, your body responds almost as if you were allergic to your baby’s blood.
Since there’s always an intermingling of your blood and baby’s, these antibodies can cross the placenta and attack baby’s blood, breaking down the red blood cells and causing anemia, or low blood cell count, which in turn can lead to some serious complications. The good news is, there are relatively easy ways to prevent this breakdown from every occurring.
Prevention starts by getting your blood (and your partner’s blood) tested with Rh antibody screening. Most of us (about 85%) are Rh positive to begin with. If you’re negative and your partner is positive, you may be given an injection of an Rh immunoglobulin, which can prevent your body from putting out the harmful antibodies. Keep in mind that this needs to be given with each pregnancy, and Rh-negative women should also receive treatment after a miscarriage, ectopic pregnancy or induced abortion to prevent the antibodies from developing for future pregnancies.