Anti‐U and haemolytic disease of the fetus and newborn

Abstract

The red cell alloantibody, anti-U, is uncommon but is a recognised cause of haemolytic disease of the fetus and newborn. We describe six pregnancies complicated by the presence of maternal anti-U, and review nine other well-documented cases. In these 15 cases severe haemolytic disease occurred only with titres of 2 1/512, and titres as high as 1/4000 were not necessarily associated with significant haemolysis. We recommend that an anti-U titre of 2 1/128 or more at 2 17 weeks of gestation is an indication for assessment of haemolysis in the fetus. Amniocentesis is the preferred initial investigation.

MNS Blood Group System

“…In one case the transfused cells responsible for the reaction were S − s − U+ var , the U antigen being too weak to be detected during compatibility testing [184] . Several examples of anti -U causing HDFN are reported, including one resulting in stillbirth [533] .…”

Transfusions of least‐incompatible blood with intravenous immunoglobulin plus steroids cover in two patients with rare antibody

“…Anti‐U is an immunoglobulin (Ig)G antibody, formed as a consequence of blood transfusion or pregnancy. It is known to cause hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN) . Jr a is the only antigen in the JR blood group system.…”

Anti-U antibody in pregnancy: a rare antibody causing hemolytic disease

“…Fewer than 1% of Africans are U‐negative and can produce allo‐anti‐U antibody (2). Only 14 women in 21 pregnancies have been reported as being positive for anti‐U antibodies (3–5). From the limited literature available, no direct correlation between antibody titer levels and clinical phenotype has been determined, varying from 1:4 to 1:16 000 (3–5).…”

“…Only 14 women in 21 pregnancies have been reported as being positive for anti‐U antibodies (3–5). From the limited literature available, no direct correlation between antibody titer levels and clinical phenotype has been determined, varying from 1:4 to 1:16 000 (3–5). It does appear that there is a threshold level of 1:32, below which significant hemolytic disease does not occur, while no clinically significant hemolysis has been noticed even at titers as high as 1:4 000 (3).…”

“…From the limited literature available, no direct correlation between antibody titer levels and clinical phenotype has been determined, varying from 1:4 to 1:16 000 (3–5). It does appear that there is a threshold level of 1:32, below which significant hemolytic disease does not occur, while no clinically significant hemolysis has been noticed even at titers as high as 1:4 000 (3). The lowest reported anti‐U titers associated with severe hemolytic disease requiring exchange transfusion is 1:512, but intrauterine death can occur at titers of less than 1:640 (3–5).…”