Alloimmunized Screening

This test is publicly funded for Ontario residents who are pregnant and have with certain red blood cell antibodies (anti-D, anti-C, anti-c, anti-E, or anti-K (Kell)). 

The timing of when the tests is done depends on the antibody:

• Anti-D, anti-C, anti-c and anti-E are tested from 16 weeks of pregnancy
• Anti-K (Kell) is tested from 20 weeks of pregnancy

This test uses a sample of your blood. During pregnancy, small pieces of genetic material from the placenta circulate in your blood. The lab looks at this material to determine if your baby has the blood group antigen that your antibody reacts to.

Your blood can be drawn at a community lab and sent to Mount Sinai Hospital for testing. Use our map to find a lab near you. 

How long do results take?

• Results are usually ready in about 10 business days and are sent to your healthcare provider.

What do the results means for pregnancy care?

• Antigen positive: Your baby has the blood group antigen and is at risk of hemolytic disease of the fetus and newborn (HDFN). Your provider will discuss extra monitoring for your pregnancy. This  may include blood tests to check the amount of antibody in your pregnancy, ultrasounds to measure blood flow, and a referral to a maternal-fetal-medicine (MFM)  specialist
• Antigen negative: Your baby does not have the blood group antigen and is not at risk of HDFN. No change to your prenatal care is needed. Your health-care provider will continue to provide routine prenatal care.

What if the test cannot give a result?

• Sometimes the test cannot give a result. Another blood sample may be requested to repeat the test, or it may be recommended to treat your pregnancy as if your baby has the antigen and provide closer monitoring.

What happens after delivery?

• After delivery, your baby’s blood group is confirmed using a blood sample from the umbilical cord, which helps guide any newborn care needed.

Results are usually ready in about 10 business days and are sent to your healthcare provider.

After delivery, your baby’s blood group is confirmed using a blood sample from the umbilical cord, which helps guide any newborn care needed.