The Rh Factor and Pregnancy

What is the Rh Factor?

The Rh Factor is a protein that can be found on the surface of red blood cells. If your blood cells have this protein, you are Rh-positive (Rh +). If your red blood cells do not have this protein, you are Rh-negative (Rh -). The Rh Factor is inherited, meaning it is passed from the individuals who created the baby. If either individual is Rh +, the baby may be Rh + or Rh -. Only if both individuals are Rh -, the baby will also be Rh -.

Can Rh status cause problems during pregnancy?

Yes. During pregnancy, problems can occur if you are Rh – and your unborn baby is Rh +. If this occurs, it is called Rh incompatibility. If a pregnant individual is Rh +, Rh incompatibility cannot occur.

How do I know if I am Rh Negative (Rh -)?

All pregnant individuals will be tested for their Rh status through a blood test.

What happens if there is Rh incompatibility?

The body’s immune system makes antibodies to proteins that are not the same as the proteins in their own body. If an unborn baby’s Rh + blood gets into the bloodstream of a pregnant individual who is Rh -, the individual can make Anti-Rh Antibodies. Once, anti-Rh antibodies are made they can cross the placenta and destroy the unborn baby’s red blood cells.

Rh incompatibility can lead to a type of anemia in the unborn baby in which red blood cells are destroyed faster than the body can replace them. This can lead to serious and even life-threatening health problems in an unborn baby or newborn.

Can the Rh Factor cause problems during my first pregnancy?

Health problems usually do not occur during the first pregnancy of an individual who is Rh – with Rh + baby because their body does not have a chance to develop a lot of antibodies. 

However, if preventative treatment is not given during the first pregnancy, and the individual later becomes pregnant with Rh + baby, more anti-Rh antibodies will be made even faster. This puts any future unborn baby at risk

Can I still develop antibodies if my pregnancy is not carried to my due date?

Anti-Rh antibodies can be made after a miscarriage, ectopic pregnancy, or a termination/abortion. There is a risk of problems if preventative treatment is not received.

Can Rh incompatibility be prevented?

Yes. The goal of preventive treatment is to stop a pregnant individual who is Rh – from making Anti-Rh antibodies in the first place. This is done by giving blood produced called Rh Immune Globulin (Rhlg). Rhlg can be given by injection (needle in the muscle or vein). This will then prevent problems in a future pregnancy.

When is Rhlg given?

Rhlg is routinely given to pregnant individuals who are Rh – in the following situations:

  • at approximately 28 weeks of pregnancy.
  • within 72 hours after birth of Rh + (positive) baby.
  • after a miscarriage, ectopic pregnancy or termination of pregnancy.
  • after procedures such as amniocentesis, Chorionic villous sampling (CVS), fetal blood sampling or fetal surgery.
  • after bleeding during pregnancy.
  • after any trauma such as a fall, car accident or blow to the abdomen.
  • after any attempts to manually turn an unborn baby from a breech position.
How safe is Rhlg?

Rhlg is safe. It is approved by Health Canada and the World Health Organization for preventing the development of anti-Rh antibodies in Rh –pregnant individuals. It has been widely used since the 1960’s. Rhlg is made from pools of human plasma (plasma from many donors). The part of the plasma that contains the anti-Rh antibodies is separated out. Rhlg (as with all blood products) has a very slight possibility of transmitting viral diseases (Hepatitis B, Hepatitis C and HIV). All donated blood must test negative for viral diseases before it can be used and Rhlg manufacturing processes include a special filter and solvent – detergent to remove viruses.  If Rhlg is given in an injection to a muscle, it could lead to slight bleeding, bruising and tenderness at the injection site.

Do I have to get Rhlg?

You will be asked to sign a consent form to show that you agree to receive this injection and understand the reason why it is required. You may withdraw your consent at any time.