Accessibility Tools

What is the Rh Factor?

Rh factor indicates the presence of a particular protein on the surface of the red blood cells. Most people have this protein and are referred to as Rh positive. People without it are Rh negative.

How does one get the Rh factor?

The Rh factor is inherited through the genes. If only one parent is Rh negative, the child may either be negative or positive, depending on which gene is inherited. When both parents are Rh negative, the child will not have the Rh factor.

What are the Rh factor-related problems during pregnancy?

Women who are Rh negative can have problems if they have babies who are Rh positive. As the mother’s body does not have the Rh factor, it considers the Rh protein in the baby as harmful and produces antibodies against it. This Rh incompatibility does not affect the first pregnancy much, since the mother does not produce enough antibodies. With subsequent pregnancies however, the antibodies attack the foetal red blood cells causing serious illness.

What is Rh sensitization?

When an Rh-negative mother has developed antibodies against the Rh factor, she is said to be Rh sensitized.

How does Rh sensitization occur?

Rh sensitization occurs when the mother’s blood comes into contact with the baby’s blood. Mother and child do not normally share blood systems, but some foetal blood can pass through the placenta during pregnancy, labour or at birth. Rh sensitization can also occur if you have bleeding during pregnancy, abdominal trauma, with certain procedures such as amniocentesis or chorionic villus sampling and when a baby in breech presentation is manually rotated for a normal delivery. Rh sensitization also occurs in cases of miscarriage, ectopic pregnancy or abortion.

How does Rh sensitization affect pregnancy?

The mother’s antibodies cross the placenta and attack the red blood cells of the growing foetus causing a condition called haemolytic anaemia, where new red blood cells are not produced fast enough and their numbers diminish. As a result, the foetus does not get enough oxygen, which is carried by the red blood cells and can become severely ill or even die.

How do I know if I am Rh sensitized?

Your doctor will perform an antibody screen, a blood test to determine the presence of antibodies to the Rh factor. This test is performed during the first trimester of pregnancy and again at the 28th week if you are Rh negative and possibly expecting an Rh positive baby.

Can I prevent being sensitized to the Rh factor?

To prevent sensitization, your doctor will recommend an injection of Rh immunoglobulin (RhIg) which is made from donated blood. RhIg targets Rh positive cells and prevents the production of Rh antibodies. This treatment can be given to Rh negative women to protect their babies and allow them to safely have more children.

Can RhIg help if I have already developed antibodies to the Rh factor?

If you are already Rh sensitized, you will not benefit from RhIg treatments.

When is RhIg normally given?

An Rh negative woman will receive RhIg:

  • At approximately 28 and 34 weeks of pregnancy
  • Within the first 2 days of delivering an Rh positive baby
  • If she has undergone an amniocentesis or chorionic villus sampling
  • If she has had an ectopic pregnancy, miscarriage or abortion

Can an Rh sensitized woman have an Rh positive baby?

Yes, your baby will be regularly monitored during your pregnancy. If anaemia is severe, your baby may be delivered early or may receive a blood transfusion through the umbilical cord while still in the womb. Babies who have mild anaemia will need a transfusion after delivery.

The University of Western AustraliaST John of God Health CareGlengarry Private Hospital