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Questions and answers about Rh Immune Globulin (Rhogam).

What do Rh positive and Rh negative mean?
First of all, Rh describes a factor (also called an antigen) that is found on the red blood cells of most people. Because the Rh factor was discovered during studies on Rhesus monkeys, the first two letters of the word "Rhesus" are used to identify it.

People who have the Rh factor on their blood cells are called "Rh positive". People who do not have the Rh factor on their blood cells are called "Rh negative". About 85% of the United States population is Rh positive and about 15% is Rh negative.

How do I find out if I am Rh positive or Rh negative?
A simple blood test is done whereby your blood is tested with a commercial reagent called "Anti-D". Anti-D is made up of antibodies to the Rh factor. When mixed with your blood, a reaction occurs. From this reaction, it is determined whether you are Rh positive or negative.

What effect does the Rh factor have upon pregnancy?
In pregnancy, Rh is especially important when an Rh negative woman carries an Rh positive child. Remember, when a woman is Rh negative, it means she does not have the Rh factor.

In the normal course of pregnancy, small amounts of the baby's blood get into the mother's bloodstream. When an Rh negative mother is carrying an Rh positive baby, some of the Rh positive blood from the baby gets into the Rh negative blood of the mother. This Rh positive blood from the baby acts like a "foreign substance" to the mother. To defend itself, the mother's immune system may make antibodies (Anti-Rh factor or Anti-D) to protect her from Rh positive blood.

Once the mother develops these antibodies, they will attack and destroy any Rh positive cells that are in the mother's bloodstream. In addition, these antibodies filter through the placenta into the blood of the unborn baby. The antibodies attack and destroy the Rh positive blood of the baby, which leads to anemia, and in severe cases, heart failure. Although this does not usually affect the mother's first baby, it will affect all future Rh positive children.

In order to prevent the development of antibodies, Rh immune globulin (Rhogam) can be given.

What is Rhogam?
Rhogam is a solution containing Rh antibodies, which is subjected into the Rh negative mother during pregnancy (around 28 weeks) and soon after delivery if the infant is RH positive. These antibodies destroy any Rh positive blood cells in the mother's bloodstream, which in turn prevents the mother from developing her own Rh antibodies.

Will Rhogam hurt the fetus?
No, there is no evidence that this small amount of antibody given hurts the fetus.

Why must I receive the shot during pregnancy and then after delivery?
Sometimes during pregnancy, the mother can develop Rh antibodies. By giving a Rhogam injection during the seventh month and again after delivery, the risk of developing Rh antibodies becomes less than 0.1%

Would I still need this shot if I already have Rh antibodies?
No, if you already have the Rh antibodies in your bloodstream, the shot will not protect you.

What happens after I deliver my baby?
Once the baby is born, your physician will send some blood from the umbilical cord down to the Blood Bank to be typed. A blood sample is also drawn on you to be tested again for blood type and antibodies. If your baby is Rh positive, you will need to receive another shot of Rhogam. If your baby is Rh negative, you will not need to receive the shot. Rhogam should be given within 72 hours of delivery.

Do I need to receive Rhogam after dilation and curettage?
Yes. The Rh factor is present on the red blood cells from the time you are eight weeks pregnancy. If there is a miscarriage or abortion, Rhogam is recommended.

What about after an ectopic or tubal pregnancy?
If pregnancy in an Rh negative woman terminates due to ectopic pregnancy or fetal death, a Rhogam injection should be given.

Is Rhogam necessary following an amniocentesis?
Yes, Rhogam should be given after an amniocentesis because a mother may be exposed to some of the baby's blood.

Is Rhogam safe?
Rhogam has an excellent safety record. Since 1968, more than 3.5 million women have received it. Rhogam is prepared by a process that has not been shown to transmit hepatitis or other infectious diseases such as AIDS.

Will I have a reaction to Rhogam?
Systematic reactions associated with giving Rhogam are extremely rare. Discomfort at the site of the injection has been reported, and a small number of women have noted a slight elevation in temperature.

Where can I obtain more information?
If you have any questions, please contact your physician or call the Butler Memorial Hospital Laboratory at (724) 284-4500.