You probably know that there are different blood types such as A, B, and O. There is also something called the Rh factor, which is a protein found on the red blood cells. If you have this protein, you are Rh positive. If you do not have the protein, you are Rh negative.
The Rh factor does not have an impact on a woman's general health, but it can cause problems during pregnancy if you are Rh negative.
What causes Rh factor to be a problem?
When an Rh negative person's blood comes into contact with Rh positive blood, the person with Rh negative blood may become "sensitized." This means that the body produces antibodies to fight the Rh positive blood as if it were harmful.
During pregnancy a mother and baby do not "share" blood, but blood from the baby can cross the placenta and enter the mother's system. If you have Rh negative blood, your body can react as if it were "allergic" to the baby's blood and start making antibodies.
The antibodies can get back across the placenta and cause problems for the baby. They can break down the red blood cells in the baby and cause anemia. It can become severe enough to cause serious problems such as illness, brain damage, or even death in the fetus or newborn.
Once formed, these antibodies do not go away and can affect future pregnancies as well.
Any time the baby's blood mixes with the mother's, there is a chance antibodies will be made. If an Rh negative woman has a miscarriage, abortion, or ectopic pregnancy it is possible that antibodies may be formed.
How can problems be prevented?
At the beginning of pregnancy, a simple blood test is done to find out if you are Rh positive or negative. Another part of that blood test, called an "antibody screen," will tell if you have any signs of antibodies in your blood.
If you are found to be Rh negative, your doctor will talk to you about a medication called Rhogam that is used to prevent antibodies from being produced.
Rhogam is a medicine that is injected in the muscle of the arm or buttocks. Rhogam is safe for pregnant women to use, and the only known side effects are soreness at the injection site or a slight fever. Both of these symptoms will go away on their own.
When is Rhogam used?
Rhogam is usually given to a woman with Rh negative blood around the 28th week of her pregnancy. It is often given again after the baby is born (if your baby has Rh positive blood).
Sometimes a woman with Rh negative blood has bleeding at the beginning of her pregnancy. Her doctor may instruct that she get Rhogam earlier in the pregnancy because of this bleeding.
If a miscarriage, abortion, or ectopic pregnancy occurs, Rhogam is given to prevent antibodies from forming that could affect future pregnancies.
It is important to remember that Rhogam is good only for the pregnancy during which the injection is given. Each future pregnancy will require a Rhogam injection as well.
Adapted from information provided by the American College of Obstetricians and Gynecologists
