Rh Blood Factor In Pregnancy

Largely determined by the type on antigens in blood cells,  our blood type is categorized into one of four groups: A, B, AB, or O.

Antigens (or the Rh factor) are the proteins that exist on the surface of the blood cells, and which cause a reaction from the immune system.

If antigens are present, your Rh factor will be positive, like 85% of the world; if they are not, your Rh factor will be negative.

Do you have Rh positive or Rh negative?

Have a blood test taken during your prenatal visit to determine your blood type.

If you have Rh negative and your partner has Rh positive blood, your fetus can get the Rh factor from your partner to enable it to have Rh positive. However, it can be problematic if the fetus’s blood has an Rh factor which your blood doesn’t.

Pregnancy in Rh negative mothers

Rh negative in a mother leads to the development of antibodies in the Rh positive baby. Even a small amount of your baby’s blood mixed with your blood can cause an allergic reaction in your baby.

Your body produces antibodies against the Rh antigens in your baby’s blood, which means that you become sensitized and your antibodies enter into the placenta and cause damage to your baby’s blood.

The antibodies entered into the baby’s blood lead to the breakage of red blood cells in the fetus and cause hemolytic anemia.  This condition can become more severe and cause serious illnesses like brain damage or even death of the newborn.

Sensitization occurs when Rh negative women have:

  • An ectopic pregnancy;
  • A blood transfusion;
  • Menstrual extraction or an induced abortion;
  • A miscarriage sign;
  • Chronic villus sampling.

How to prevent the problems related to Rh factor

  • Basically Rh factor can be determined with a blood test.
  • In addition to a blood test to determine your Rh factor, another blood test called antibody screen will tell Rh negative women whether they have developed antibodies for Rh positive blood.
  • An injection or Rh immunoglobulin (Rhlg), a blood product that helps prevent sensitization in an Rh-negative mother.

When is Rhlg recommended?

You can use Rhlg during pregnancy and after delivery.

  • If you are an Rh negative mother and have not been sensitized, your doctor will recommend Rhlg during the 28th week of pregnancy in order to avoid sensitization for the remaining period of the pregnancy.
  • Rhlg treatment is only good for the pregnancies in which it is administered. Each pregnancy with an Rh positive child needs a new dosage of Rhlg.
  • If the Rh negative women have previously had a miscarriage, induced abortion or ectopic pregnancy, treatment is necessary to prevent the possibility of developing antibodies that can attack the Rh positive baby in future.
  • If the newborn baby has Rh positive blood, you should receive a dosage of Rhlg to prevent the development of antibodies to the Rh positive cells you get from your baby before and during the delivery.


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