Optimizing Care and Protecting Future Families

Currently, up to 40% of pregnant Ontarians who are RhD negative (i.e. do not have the D antigen on their red blood cells) are receiving RhD Immune Globulin (RhIG) – a blood product they don’t actually need. A new test is going to change that – making patient care more precise and the health system more efficient.

Why is having an RhD negative blood type a problem?

Being RhD negative isn’t a problem unless you are pregnant and your baby’s blood type is different (e.g. RhD positive). This ‘mismatch’ of blood types can lead to complications.  

Sometimes the baby’s blood and the pregnant person’s blood can mix during pregnancy and birth. When this happens, the pregnant person’s immune system mislabels the baby’s red blood cells as ‘foreign’ and starts creating antibodies against them. In future pregnancies, the primed immune system of the pregnant person can attack the ‘foreign’ red blood cells if the baby is RhD positive. If the baby's attacked red blood cells are broken down faster than they can be made, a life-threatening condition called hemolytic disease of the fetus and newborn (HDFN) can occur.

HDFN can cause jaundice (yellowing of the skin and eyes), anemia (low red blood cell count), and in severe cases, heart failure or death.

To prevent HDFN, a human blood product called RhD Immune Globulin (RhIG) (also known as RhoGam or WinRho) is given to the pregnant person. RhIG stops the pregnant person’s immune system from creating antibodies against the baby's red blood cells.

Protective Measures are not Specific

HDFN can be very serious. In current practice, all RhD negative pregnant people receive the RhD Immune Globulin (RhIG) injection (even though the RhD status of the baby is unknown). But in 40% of these cases, the lab test performed after birth shows there was no mismatch – the baby was RhD negative. In these cases, pregnant people received a human blood product they didn’t actually need.

For RhD negative pregnant people who have already developed anti-D antibodies, whether during their current or prior pregnancy(ies), the RhIG injection serves no purpose. These individuals (about 2,000/yr in Ontario) are already at risk of HDFN and their pregnancies need extra monitoring.  This may look like extra doctor’s appointments, referrals to Maternal Fetal Medicine (MFM) specialists and additional blood work and ultrasounds. All of this monitoring, however, may be unnecessary and could stop half way through pregnancy or even sooner if it is determined that the developing baby does not have the antigen to which the mother/ pregnant person is sensitized.

New Tests will Allow for Improved, Personalized Healthcare

To personalize care and improve system efficiency, Ontario Health, in a recent Health Technology Assessment, has recommended publicly funding two tests that check the unborn baby’s blood type in these scenarios:

  1. When the pregnant person is RhD negative;
  2. When the pregnant person has already developed antibodies towards specific antigens.

These two tests are known as fetal blood group genotyping (FBGG).

How do these tests work?

By taking a blood sample from the pregnant person, lab scientists can see tiny pieces of the unborn baby's DNA and predict if the baby's blood type is positive or negative for the antigen in question.

Checking the baby's blood type early in pregnancy, will help doctors identify if there is a mismatch and provide the RhD negative pregnant person with RhIG (protecting the baby from HDFN). If the test reveals that the blood types are the same (and therefore the baby is not at risk of HDFN), the pregnant person doesn’t need the injection.

For the pregnant person that has already developed antibodies (alloimmunized or sensitized), if the blood test indicates the unborn baby does not have the specific antigen towards the antibodies that the pregnant person has developed, extra monitoring and treatment can stop, along with many additional physician appointments.

For more detailed information about these tests see: A Health Technology Assessment - Noninvasive Fetal RhD Blood Group Genotyping

Prenatal Screening Ontario will roll out the new publicly-funded tests

Prenatal Screening Ontario (PSO) is uniquely positioned to plan for and implement the two new tests that will determine the fetal blood type. The PSO team has been busy behind the scenes - getting ready for the provincial roll-out of these new tests in 2025.

Work includes:

  • Selecting a Lab Vendor(s): PSO is choosing a lab(s) to perform the tests.
  • Forming Working Groups: PSO is setting up working groups to guide implementation efforts.
  • Planning for Service Delivery: PSO is creating a plan to ensure the tests are provided effectively.
  • Creating Educational Materials: PSO is developing materials to educate healthcare providers and the public about these new tests.

Visit the PSO website to learn more about how PSO coordinates cohesive, high-quality screening for pregnant people in Ontario.