I am RhD negative

Your blood type is determined by the proteins, called antigens, on the surface of your red blood cells. The combination of antigens present, determines your blood type.  There are many different blood group antigens on red blood cells but the most important are the ABO antigens and the Rh antigens.

The RhD antigen is very important in pregnancy.

  • If the RhD antigen is present, your blood type is “Rh positive (+)”
  • If the RhD antigen is absent your blood type is “Rh negative (-).”

A baby's blood type is inherited from its parents.

  • If both parents are RhD negative, the baby will be RhD negative.
  • If one or both parents are RhD positive, the baby may be RhD positive or RhD negative.

RhD can cause problems in pregnancy if you are RhD negative and your baby is RhD positive. This mismatch is called RhD incompatibility.

If your baby’s RhD positive blood mixes with your RhD negative blood you may make antibodies (anti-D). This is called RhD alloimmunization or sensitization. This may happen during pregnancy or at delivery.

Once these antibodies develop, they persist. In a future pregnancy, if the baby is RhD positive the antibodies may cross through the placenta, attach to the baby’s red blood cells and result in break down and clearance of the cells. This condition is called hemolytic disease of the fetus and newborn (HDFN).

Your health-care provider will order prenatal blood work to find out your ABO/RhD blood type and check for antibodies.  This is one of the routine blood tests done early in pregnancy.  This test is usually done after 8 weeks of pregnancy (preferably between 11-14 weeks).

If your blood test shows that you are RhD negative and you do not have D antibodies, your next step is to have a blood test called Fetal RHD screening to find out your baby's RhD type.  The results will help determine if you need a treatment called RhD immune globulin (RhIG) to prevent alloimmunization to the RhD antigen.

 

 

If your baby is RhD positive, a treatment called RhD immune globulin (RhIG), is recommended to prevent your body from making antibodies against your baby's RhD type.  RhIG is a human blood product given by injection, that helps to stop your body from making anti-D antibodies that could lead to a serious condition called hemolytic disease of the fetus and newborn (HDFN).

 

RhIG is an injection given to RhD negative pregnant individuals: RhIG is NOT needed if:
  • around 28 weeks of pregnancy,
  • in situations where there is bleeding, trauma, or if certain tests are done in pregnancy (e.g. amniocentesis) and
  • after delivery.
  • you are RhD positive
  • your baby is RhD negative like you or
  • you already have anti-D antibodies.

 

The results of Fetal RHD screening will determine if you need RhIG treatment during your pregnancy.

PSO Infoline

Our genetic counsellors and screening specialists are available Monday to Friday from 9:00 am - 3:00 pm EST to answer your questions about prenatal screening.

Please note that prenatal screening tests have to be ordered through a health-care provider, and we cannot organize this testing.

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