Rh Sensitization and Induced Abortion

To the Editor A recent study posited that analysis of fRBCs in pregnant individuals who had previous induced abortions at less than 12 weeks ’ gestational age could be used to recommend discontinuation of Rh immunoglobulin prophylaxis in a subset of patients. While this research provides valuable insights into the complex issue of maternal alloimmunization, it does not establish a clear link between fRBC levels and the most important o utcome—hemolytic disease of the fetus and newborn (HDFN). First, the study’s premise relied on the establishment of a specific threshold of fRBC transfer required to induce alloimmunization. While the authors set a “conservative” threshold of 125 fRBCs per 5 million total RBCs, there is unce rtainty regarding the exact fRBC concentration necessary to trigger alloimmunization. The 0.1-mL blood volume used as the basis for their development of the threshold of 125 fRBCs per 5 million RBCs was originally derived in a study performed in 1965, in which 0.1 mL of fRBCs was injected every 6 we eks into 15 antibody-free female participants until antibodies were detected. However, subsequent studies showed that alloimmunization occurred after exposure to fewer fRBCs. Notably, sensitization has been reported following apheresis platelets that typically contain 0.0005 mL of fRBCs or less.
Source: JAMA - Category: General Medicine Source Type: research