Members of the College of American Pathologists (CAP) highlight the need for improvement in quantitative laboratory assays for fetomaternal hemorrhage used when performing Rh immunoprophylaxis. In 2008, the CAP developed a publically available RhIg dose calculator (www.cap.org). However, a 2012 analysis found that despite prior efforts to standardize RhIg dose recommendations, the accuracy and precision of laboratories quantifying fetomaternal hemorrhage and calculating doses of RhIg for immunoprophylaxis remained unsatisfactory. Among laboratories using acid-elution methods (96.1% of laboratories), 46.6% recommended inadequate doses of RhIg and 29.1% recommended an overdose. In a commentary in the journal Transfusion, the CAP emphasized the need for increased access for more precise methods of measurement, such as flow cytometry. CAP suggested that new models of hematology analyzers may incorporate capabilities for immunocytometric quantification of fetomaternal hemorrhage.