We used to do weak D tests with post-partum RhIG workups because we did a full blood type and antibody screen with them to make sure mom was a candidate. (Also, to look for massive FMH that would cause an Rh neg mom to look like a weak D but that was before the Fetal Screen/rosette test was invented.) In those days, weak D pos moms were not RhIG candidates, but they are now. With modern reagents, those who react only at AHG anti-D testing are likely to be partial D VI and more likely to make an anti-D. We would rather not find them and just call them Rh negative from the IS test so we don't do weak D testing routinely on obstetric patients. We all dropped the antibody screen when we started using sensitive techniques like gel that picked up the 28 week RhIG dose at the time of delivery. If the screen was negative, you gave RhIG; if the screen was positive with anti-D (unless it was super strong) you still gave RhIG so why do the test if it won't change the treatment? Now we do weak D tests only if the Fetal Screen is "diffusely positive" to understand if a weak D is causing it. We get surprisingly few of them. Of course we do weak D tests on the babies of Rh neg moms.