No difference in alloimmunization of pregnant adults with sickle cell disease exposed to chronic versus on‐demand transfusions: A two‐center retrospective cohort study

Abstract Background Pregnant people with sickle cell disease (SCD) experience high morbidity and mortality, even when RBC transfusion is safe and available. There is a lack of consensus on transfusion use partly due to concern for alloimmunization. This study examined alloimmunization in SCD pregnancies managed with chronic transfusion therapy (CTT) versus on‐demand transfusion (ODT). A secondary aim was to quantify the proportion of SCD pregnancies that met guideline indications for CTT that received CTT in pregnancy. Study Design This is a two‐center, retrospective study of pregnancy in SCD over two decades. We compared alloimmunization between those who received CTT versus ODT by examining the Sickle Cell Pregnancy and Reproductive Knowledge Syndicate database. A secondary analysis applied American Society of Hematology (2020) and/or British Society for Haematology (2021) criteria for CTT in pregnancy to calculate guideline compliance. Results Among 145 subjects, 26 received CTT and 119 received ODT. Alloimmunization incidence was 4%, with no significant difference by transfusion group (1/26 CTT vs. 5/119 ODT, p = 1.0). Five ODT subjects became alloimmunized (5/46). One CTT subject was alloimmunized (1/26) after receiving an unplanned ODT. Of all pregnancies, 87% met ASH criteria and 65% met BSH criteria for CTT, while 20% received CTT. Discussion For patients with SCD in pregnancy, CTT may not pose a greater alloimmunization risk than ODT. CTT may be underutilized for SCD in pregnancy. Our study is limited by incomplete data and variable antigen matching practices. Prospective research will help establish the appropriate role of CTT in SCD pregnancies.