Laboratory Assessment of Fetomaternal Hemorrhage is Improved Using Flow Cytometry

Fetomaternal hemorrhage (FMH) occurs normally throughout pregnancy. If there is a significant difference in the red blood cell antigenicity between the fetus and mother, this results in allosensitization of the maternal immune system. Accordingly, detection and accurate enumeration of fetal red blood cells (RBCs) in Rh or D antigen-negative women is an essential part of the management of those patients with FMH treated with Rh immune globulin preparations. There are various methods for FMH detection, and these are discussed and compared with flow cytometric methods of FMH detection. Flow cytometric methods are presented to be superior in accuracy, though there are several factors that can cause variability of results. Also, though superior, flow cyometric assessment of FMH has not increased in the United States to the level that is seen in the United Kingdom and Australia. Possible reasons for this are discussed.