Of the main D variants, a female with partial D (or partial weak D) may develop anti-D to the D epitopes that she lacks. Moreover, partial D red cells adsorb little anti-D, thus leaving enough free RhIg to suppress immunization.
However, most laboratories do not routinely differentiate between D variants and instead rely on routine tests and associated test protocols to determine a mother's Rh status for the purposes of RhIg administration.
Policies differ between countries and even within countries.
- Some labs do not test pregnant women for weak D and rely on routine D typing to determine Rh status.
- Some labs perform weak D tests on pregnant women who appear to be Rh negative and, if weak D, do NOT inject with RhIg.
- Some labs perform weak D tests on pregnant women who appear to be Rh negative and, if weak D, inject with RhIg based on the possibility that they may be partial D and capable of forming anti-D.