SBriggs

Thanks for the input thus far.  I did email AABB for a definition so if I get a response from them I will share on this thread as well. 

This is from the British Committee for Standards in Haematology:
 
"Maternal samples for confirmatory ABO and Rh D type and FMH testing should be collected after sufficient time has elapsed
for any FMH to be dispersed in the maternal circulation. A period of 30–45min is considered adequate (Mollison et al.,
1997) and the samples should ideally be taken within 2h of delivery primarily to ensure that the sample is taken prior to
woman’s discharge from the hospital (RCOG, 2011)."
 
Ref: TRANSFUSION  MEDICINE, 2014, 24, 8 - 20

The product insert for RhoGAM used to reference specimen collection 1 hour after delivery, but doesn't anymore.
 
The product insert for Immucor's Fetal Bleed Screening Test states that "it is best to wait about an hour after delivery to allow any fetal blood to mix thoroughly in the maternal circulation, but the sample should be collected as soon as possible thereafter". The reference for that is Judd WY, Luban NLC, et al. Prenatal and perinatal immunohematology: recommendations for serologic management of the fetus, newborn infant, and obstetric patient. Transfusion 1990; 30:175-183.
 
Our policy says to draw the patient 1 hour after delivery, if possible, or as soon as possible after that. We consider the order to be an urgent draw - testing is routine. Administration is within 72 hours or before patient dismissal, as everyone as stated.

I believe many eons ago the package insert for some of the fetal screen tests referenced the one hour time period but I do not have access to those to confirm.  I believe the rationale was/is that if the fetal cells are ABO incompatible with the mother, the fetal cells will be destroyed by the maternal antibodies so a falsely low value of the amount of fetal bleed may be obtained.  I know everyone here understands that ABO incompatible fetal cells actually provide some natural prophylaxis to the mother for the prevention of immunization to D so may be less of an issue if you're doing the test simply to determine RhIgG dosing.  The same rationale could apply for early removal of D-positive fetal cells from the maternal circulation due to the presence of any prophylactic/antenatal anti-D.  However if the test is being performed to determine the amount of fetal bleed as a diagnosis test for the treatment of the infant, one should be aware of these factors that may affect the result.