Hands, Katie

Abstract Background Anti‐M antibodies were described as rarely eliciting hemolytic disease of the fetus and newborn (HDFN) in pregnancy. More recent literature, primarily from Asia, reports severe HDFN attributed to maternal anti‐M. The objective of this study is to determine if there is a difference in the frequency and/or severity of anti‐M HDFN among subjects who self‐report as Asian compared to non‐Asian. Methods Retrospective data were collected from 18 sites. Fetuses/neonates affected by HDFN were categorized as unaffected, mild, moderate, or severe based on clinical management and outcomes. Results Anti‐M was identified in 557 obstetric patients. Among 332 neonates with complete data for analysis, anti‐M was detected in isolation during the pregnancies of 210 (63.3%) neonates; 198 (94.3%) were unaffected by HDFN. The overall frequency of HDFN was 6.5% (2/31) in Asian patients and 5.6% (10/179) in non‐Asian patients. The frequency of severe HDFN was 6.5% (2/31) among Asian patients and 0.6% (1/179) among non‐Asian patients. Among non‐Asian patients, eight (4.5%) were mild and one (0.6%) was moderate. Of 63 pregnancies with anti‐M and ABO incompatibility, 6 (9.5%) were associated with mild HDFN and 57 (90.5%) were unaffected. Of 49 pregnancies with anti‐M and non‐ABO antibody(s), 6 (12.2%) were associated with mild HDFN and 43 (87.8%) were unaffected. One case (10.0%) of HDFN (mild) occurred in the presence of anti‐M, additional antibody(s), and ABO incompatibility. Conclusion In this study, severe anti‐M HDFN was rare in non‐Asian subjects. There is a signal that Asian patients are at greater risk for severe anti‐M HDFN.

Abstract Background Rho(D) immune globulin (RhIg) is used to reduce RhD alloimmunization in pregnancy. This study describes potential causes for RhD alloimmunization after the development and implementation of RhIg. Study Design and Methods This retrospective descriptive study investigated RhD‐negative patients born in 1965–2005 with anti‐D newly identified during 2018–2022. Transfusion, pregnancy, intravenous drug abuse, and transplantation were considered potential alloimmunization sources. Results There were 1200 study patients (852 females; 348 males) at 30 institutions in 5 countries (USA, Canada, UK, New Zealand, Brazil). Most patients had a single potential source of alloimmunization identified (857/1200, 71%), most commonly pregnancy among females (537/852, 63%) and transfusion among males (180/348, 52%). When multiple potential sources were included, males were more likely than females to have a history of transfusion (235/348 [68%] vs. 149/852 [17%], p < .0001) and confirmed or suspected intravenous drug abuse (100/348 [29%] vs. 138/852 [16%], p < .0001). Among females with a history of pregnancy, 119/718 (17%) had healthcare access issues, 120/718 (17%) had pregnancy in a country where they may not have received RhIg, and 21/718 (3%) refused RhIg. Among patients with a history of transfusion, males were more likely than females to have received RhD‐positive red blood cells or whole blood (143/235 [61%] vs. 30/149 [20%], p < .0001) and/or platelets (84/235 [36%] vs. 19/149 [13%], p < .0001). Discussion Pregnancy was the most frequently identified potential source of RhD alloimmunization among females. Transfusion was most frequent in males. Intravenous drug abuse as a common potential source among patients with RhD alloimmunization merits further study.