RH Positive or Negative: What’s the Difference?
Rh stands for Rhesus. The Rhesus factor refers to a certain protein found on red blood cells. If this protein is present, a person is Rh+. If the protein is absent, a person is Rh-. Approximately 85 percent of the population is Rh+, while the other 15 percent is Rh-. Whether a person is Rh+ or – doesn’t have any effect on his or her health, however when an Rh- mother is carrying an Rh+ baby, there can be issues.
When is being Rh- a problem?
Being Rh- becomes a problem when a pregnant mother who is Rh- is carrying a baby who is Rh+. The Rh protein is one of many antigens on the surface of blood cells that generate a response from the immune system. If Rh+ blood comes in contact with the Rh- blood, the person with Rh- blood (in this case the pregnant mother) will produce antibodies to fight the Rh protein, as if it were a foreign body. This is called sensitization.
Although a pregnant mother and unborn child do not share blood systems, a small amount of blood from the fetus can cross the placenta and enter the mother’s system. A small number of pregnant mothers will make antibodies that will attack and break down the Rh+ blood cells. These antibodies can also cross the placenta and start attacking the blood cells inside the fetus resulting in anemia, which can lead to serious illness, brain damage or even death of the fetus or newborn.
A woman can become sensitized if her Rh- blood has come in contact with Rh+ blood through:
- Induced abortion
- Ectopic pregnancy
- Blood transfusion
- Chorionic villus sampling (CVS)
- Bleeding during pregnancy
- Blunt trauma to the abdomen during pregnancy
- Rotation of a baby in breech position before labor
“In a first pregnancy with an Rh-positive fetus, the baby often is born before the woman’s body develops many antibodies, so there may be no serious problems. In a second pregnancy with an Rh-positive fetus, these antibodies are more likely to cause anemia in the fetus. In most cases, the condition becomes worse in later pregnancies” (ACOG).
The Rh Blood Test
The Rh blood test (antibody screen) is a simple blood test that is often administered during the first prenatal visit. If the results come back that your baby is Rh+, then it will be recommended for the pregnant mother to receive an RhIg injection at 28 weeks, which will prevent her body from producing antibodies during the last three months of pregnancy.
RhIg stands for Rh Immunoglobulin. It only works if the mother hasn’t already become sensitized. This injection is usually given in the arm or in the buttocks. Another injection may be recommended if the pregnancy goes past the due date, and shortly after birth.
The RhIg injections need to be given at each subsequent pregnancy, and following any of the situations listed above where contact with Rh+ blood has or might have occurred.
“If the antibody screen shows that you’re already producing antibodies, an injection of Rh immune globulin won’t help. Your baby will be carefully monitored. If necessary, he or she may be given a blood transfusion through the umbilical cord during pregnancy or immediately after delivery.” (MayoClinic)
Darlene Oakley is a freelance writer for EmpowHER.com.
Rh Factor. American Pregnancy Association. Web. Mar 19, 2012.
The Rh Factor: How It Can Affect Your Pregnancy FAQ. The American College of Obstetricians and Gynecologists. Web. Mar 19, 2012.
Rh factor blood test. Mayo Clinic. Web. Mar 19, 2012.