The Rh Factor Simply Explained
The Rh Factor is a substance that occurs naturally on the red blood cells of some individuals. If you have the Rh Factor you are termed ‘Rh Positive’. If you lack the Rh Factor, you are termed ‘Rh Negative’. Everyone is either Rh Positive or Rh Negative. One type is neither worse nor better than the other – only different.
The Importance of the Rh Factor
Your Rh Factor is important to you in two situations: when receiving a blood transfusion, and when you, if you are an Rh Negative woman, become pregnant. If the father of your baby is Rh Positive, the baby can inherit his Rh Factor. If the baby is Rh Positive while you are Rh Negative, there is a chance that you will be stimulated to produce antibody against the Rh Factor.
Rh Types of Different Matings
| # | Father Rh Positive | Father Rh Negative |
| Mother Rh Positive | Baby Rh Positive or Rh Negative | Baby Rh Positive or Rh Negative |
| Mother Rh Negative | Baby Rh Positive or Rh Negative | Baby Rh Negative |
Rh Factor Frequencies
Rh Positive: 85%
Rh Negative: 15%
At the time of delivery or if the baby is lost through miscarriage, some of the baby’s red blood cells will likely enter your bloodstream. It is also possible that the baby may bleed intermittently into your bloodstream throughout the pregnancy. If this happens, your body will sense the presence of the ‘foreign’ Rh Positive cells and produce substances known as antibodies to destroy them. These antibodies are similar to those produced against viruses or bacteria. And are an important part of the defence mechanism of the body. Once you have produced these antibodies, they will persist in your body for life.
Should you again become pregnant with an Rh Positive baby, these same antibodies in your blood stream will enter the blood fo your baby. They will attack the baby’s red blood cells and cause them to be destroyed. This can produce serious complications and abnormalities in your baby – even death of the unborn baby.
Hemolytic Disease of the Newborn
After delivery, an infant suffering from hemolytic disease of the newborn may be jaundiced and anemic, or suffer damage of the brain and central nervous system. Extensive medical care including exchange transfusions may be required. (Exchange transfusion is a process of removing the baby’s blood and replacing it with blood which will survive normally). This usually stops the destruction of the baby’s blood and gives the infant a chance to survive. The risk of hemolytic disease of the newborn is slight with the first pregnancy but increases with each successive pregnancy.
Prevention of Hemolytic Disease of the Newborn
There is now a simple method that can prevent this disease from occurring in your baby – by the mother receiving an injection of Rh Immune Globulin.
Rh Immune Globulin is a specially prepared gamma globulin which has high levels of antibodies against the Rh Factor. If you are Rh Negative and receive this therapy within 72 hours after delivery or loss of your Rh Positive baby, the injection will destroy the Rh Positive red blood cells in your system. In rare situations, (about 1% of pregnancies,) the mother will have already been sensitized to producing antibodies prior to delivery of the baby. It is believed this is because the baby has bled into the mother’s bloodstream during pregnancy. It has been shown that this failure rate can be eliminated if an additional injection of Rh Immune Globulin is given at about 28 weeks gestation.
If Rh Immune Globulin is given as recommended your body should not make antibodies against the Rh factor. However because Rh Immune Globulin lasts in your body only for about four months, you should receive Rh Immune Globulin at about 28 weeks gestation, as well as after delivery, in every pregnancy.
Rh Immune Globulin protection is of value only for women who do not already have Rh Factor anti-bodies in their blood from a previous pregnancy, miscarriage or blood transfusion. Women who have already developed the antibodies cannot be helped by Rh Immune Globulin. That is why it is important for you to have an injection of Rh Immune Globulin after each birth, miscarriage or abortion.
Trauma During Pregnancy
There is an increased risk that the baby will bleed into your bloodstream if there is trauma to the placenta. Some of the situations where this might occur includes a serious fall, a car accident, amniocentesis and obstetrical complications such as placenta previa. If any of these situations occur during your pregnancy, a second antenatal injection of Rh Immune Globulin should be given.