Rh Antibody Titre

Function

The Rh Antibody Titre test measures the concentration of antibodies against the Rh factor (specifically the D antigen) in a person's blood. This is most critical in Rh-negative pregnant women who may have been exposed to Rh-positive fetal blood, a process known as sensitization.

Why it is Ordered

This test is a staple of prenatal care for Rh-negative mothers. It is used to monitor for 'Rh Isoimmunization.' If a mother develops these antibodies, they can cross the placenta and attack the red blood cells of an Rh-positive fetus, leading to Hemolytic Disease of the Fetus and Newborn (HDFN).

Associated Conditions

• Rh Sensitization: Occurs after a previous pregnancy, miscarriage, or blood transfusion where Rh-negative blood met Rh-positive blood.
• Hemolytic Disease of the Fetus and Newborn (HDFN): A condition that can cause fetal anemia, jaundice, brain damage (kernicterus), or even fetal death (hydrops fetalis).
• Transfusion Reactions: Occurs if an Rh-sensitized person receives Rh-positive blood.

Monitoring Protocol

If the titre is low (e.g., 1:4), the pregnancy is monitored closely with repeat testing. If the titre rises to a critical level (often 1:16 or higher), specialized procedures like middle cerebral artery (MCA) Doppler ultrasounds are performed to check for fetal anemia.