How Can Rh Sensitization Affect The Pregnancy?

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Rh Factor

There are four major blood groups: A, B, AB, or O. Blood types are differentiated by the types of antigens on the blood cells. Antigens are proteins on the surface of blood cells that can cause a response from the immune system. The Rh factor is simply a type of protein on the surface of red blood cells. Those who have the Rh factor are regarded as Rh-positive and those who do not have the Rh factor are Rh-negative. Rh senstization is considered to be a serious issue during pregnancy which require attention.

How to know if Rh negative or Rh positive?

As part of the prenatal care checkup, a blood test will be conducted to find out the blood type. If the blood lacks the Rh antigen, it is called Rh-negative and if it has the antigen, it is called Rh-positive. When the mother lacks Rh antigen (Rh-negative) and the father possess Rh antigen (Rh-positive), the fetus can inherit the Rh factor from the father which makes the fetus Rh-positive. Problems may arise when the fetus’s blood has the Rh factor and the mother’s blood does not have Rh factor.

Rh-negative and pregnancy

If you are Rh-negative, you may develop antibodies to an Rh-positive baby. Even if a small amount of the baby’s blood gets mixed with your blood, the body may respond allergically towards the baby. The mother’s body may make antibodies to the Rh antigens in the baby’s blood and these antibodies can cross the placenta and attack the baby’s blood.

This in turn break down the fetus’s red blood cells causing anaemia. This condition is referred as hemolytic disease or hemolytic anemia which may often lead to serious illness, brain damage, or even death in the fetus or newborn. Sensitization can occur at any time when the fetus’s blood mixes with the mother’s blood.

This may happen when the Rh-negative woman has had:

  • An induced abortion or menstrual extraction
  • A miscarriage
  • An ectopic pregnancy
  • Chorionic villus sampling
  • A blood transfusion

How to prevent problems?

  • A blood test can denote the blood type and Rh factor.
  • Another blood test called antibody screen can show if an Rh-negative woman has developed antibodies to Rh-positive blood.
  • Rh immunoglobulin (RhIg), a blood product can be injected which prevents sensitization of a Rh-negative mother.

When is RhIg used?

RhIg can be used even during pregnancy and after delivery:

  • The doctor may suggest to receive RhIg around the 28th week of pregnancy in order to prevent sensitization for the rest of pregnancy.
  • If the baby is born with Rh-positive blood, the mother is needed to take another dose of RhIg in order to prevent her from making antibodies to the Rh-positive cells that she may receive from the baby before and during delivery.
  • Each pregnancy and delivery of an Rh-positive child requires repeat doses of RhIg.
  • Rh-negative women also need treatment after any miscarriage, ectopic pregnancy, or induced abortion in order to prevent any chance of developing antibodies that may attack a future Rh-positive baby.

Other reasons to use RhIg

  • When an amniocentesis is conducted, it may cause the fetal Rh-positive red blood cells to get mixed with a mother’s Rh-negative blood causing her to produce antibodies therefore it is necessary to inject RhIg.

An Rh-negative mother may receive RhIg after a birth, even if she decides to have her fallopian tubes tied or cut in order to prevent future pregnancies for the following reasons:

  1. The woman may decide later to try to have the sterilization reversed.
  2. There is a slight chance for the sterilization to get failed which prevents pregnancy.
  3. In case if there is a need for a blood transfusion in the future, the treatment will prevent her from developing antibodies.

What happens if antibodies develop?

Once antibodies are developed, RhIg treatment does not help. A mother who is Rh sensitized must be regularly checked during her pregnancy period to see whether the fetus is developing the condition. The baby may be delivered on time, which can be followed by a blood transfusion in order to replace the diseased blood cells with the healthy blood. In severe cases, the baby may be delivered early and give transfusions from the mother’s uterus itself.

How common is the Rh-negative factor?

  • More than 85% of people are Rh positive.
  • The Rh factor does not affect a person’s general health.
  • Problems that can occur during pregnancy due to the mismatch of baby’s blood with the mother’s blood can be prevented by a  medication called immunoglobulin (RhIg).