The Kleihauer–Betke ("KB") test is a blood test done on a pregnant woman. It is a blood test used to measure the amount of fetal blood (eg fetal hemoglobin) transferred from a fetus to a mother's bloodstream. It is named after Enno Kleihauer and Klaus Betke who described it in 1957. The test can be done during pregnancy or shortly after delivery.

Why is the Kleihauer-Betke test done?

There are several reasons to do the Kleihauer-Betke test.

• On an Rh-negative mother to determine the required dose of Rho(D) immune globulin (RhIg) to inhibit the formation of Rh antibodies in the mother and prevent Rh disease in future Rh-positive children.
• On a pregnancy where the baby shows anemia or is stillborn to see if there was fetal-maternal bleeding or hemorrhage that could explain what happened.
• In a pregnancy with decreased fetal movements