Red cell alloimmunization in pregnancy: a study from a premier tertiary care centre of Western India

Rate of clinically significant red blood cell antibody seroconversion in pregnancy

OBJECTIVE

To determine the rate of clinically significant red blood cell (RBC) antibody seroconversion in pregnancy and associated risk factors and neonatal outcomes.

METHODS

This is a retrospective cohort study of all deliveries within a large multi-hospital system from July 2016 to March 2023. Deliveries with a missing RBC antibody screen on admission for delivery were excluded, as were deliveries with a positive antibody screen on admission for delivery without a record of antecedent type and screen (T&S) in that pregnancy. Deliveries were categorized as 1) not possessing clinically significant antibodies (which includes those with a negative antibody screen, evidence of passive immunity solely due to Rh(D) immune globulin (RhIG), or possessing only non-clinically significant RBC antibodies); 2) previously alloimmunized (i.e. pregnancies that demonstrated clinically significant antibodies on the first T&S, regardless if they accrued additional antibodies throughout the pregnancy); or 3) seroconverted (i.e. no clinically significant antibodies on the first T&S with subsequent development of alloimmunization with clinically significant antibodies). For neonates born to seroconverted patients with clinically significant antibodies, neonatal outcomes such as initial hemoglobin, need for transfusion, and neonatal intensive care unit (NICU) admission were ascertained via chart abstraction. All records were linked with an existing validated database, inclusive of maternal characteristics and pregnancy outcomes, and comparisons were made between three categories based on antibody status with a sub-analysis of two categories. Bivariate analysis was performed with Chi-square for categorical and Wilcoxon rank-sum or Kruskal-Wallis test for continuous variables.

RESULTS

There were 58,912 pregnant individuals with 71,384 eligible deliveries during the study period, with 67,570 deliveries remaining after data linkage. Of these, 67,209 (99.5%) deliveries had a negative or non-clinically significant antibody screen at delivery. Of the remaining 361 (0.53%) deliveries, 185 (0.27%) were previously alloimmunized and 176 (0.26%) seroconverted in pregnancy. Among pregnancies demonstrating seroconversion, the most common newly acquired antibodies were anti-E, anti-c, anti-JkA, anti-C, anti-D, anti-M, anti-K, and anti-S. Among the 176 pregnancies complicated by seroconversion, there were four unexplained fetal losses, none of which were attributable to HDFN. Among the 178 liveborn neonates born to the 176 pregnancies demonstrating seroconversion, three (1.7%) infants had initial hemoglobin <13.5 mg/dL, four (2.2%) required postnatal transfusion but all were unrelated to HDFN, and 34 (19.1%) required NICU admission. When comparing deliveries demonstrating seroconversion with those with a negative antibody screen at delivery, advanced maternal age and increasing gravidity and parity were most strongly associated with seroconversion.

CONCLUSION

Development of new clinically significant RBC antibodies in pregnancy occurred at a rate of 0.26% in this large cohort study with no cases of stillbirth or neonatal demise attributable to RBC alloimmunization among pregnancies demonstrating seroconversion. Advanced maternal age and increasing gravidity and parity were most strongly associated with seroconversion in pregnancy. Routine third trimester prenatal assessment of maternal antibody status may not be indicated due to low likelihood for clinically significant seroconversion.

Red Blood Cell Alloimmunization in Pregnancy: A Review of the Pathophysiology, Prevalence, and Risk Factors

This review paper provides an overview of the risk factors and laboratory testing for red blood cell (RBC) alloimmunization in pregnancy. RBC alloimmunization is a significant medical issue that can cause haemolytic disease of the fetus and newborn (HDFN), leading to neonatal morbidity and mortality. Current HDFN prophylaxis targets only Rhesus D (RhD) alloimmunization, with no effective measures to prevent alloimmunization to other RBC antigen groups. Several factors can increase the risk of developing RBC alloimmunization during pregnancy, including fetomaternal haemorrhage, RBC and maternal genetic status, and previous transfusions. Identifying these risk factors is essential to execute the appropriate management strategies to minimize the risk of HDFN. The review also discusses the laboratory methods and overview of pregnancy management. The paper highlights the importance of identifying and managing the risk factors for RBC alloimmunization in pregnancy to minimize the risk of HDFN and improve neonatal outcomes.

Magnitude of Red Blood Cell Alloimmunization Among Pregnant Women Attending Antenatal Care at Wolaita Sodo University Comprehensive Specialized Hospital, Southwest Ethiopia

Background

Maternal red cell alloimmunization occurs when a woman's immune system becomes sensitive to unfamiliar red blood cell antigens. This leads to the production of alloantibodies, which can have serious implications for the fetus and newborn. However, there is a lack of comprehensive information about the extent of red cell alloimmunization in underdeveloped countries like Ethiopia. Therefore, this study aimed to determine the magnitude of red cell alloimmunization among pregnant women attending antenatal care at Wolaita Sodo University Comprehensive Specialized Hospital from September 01 to November 30, 2022.

Methods

In this institutional-based cross-sectional study, 422 pregnant women were participated and recruited using a systematic random sampling technique. Data on sociodemographic characteristics, obstetric history, and other clinical information were collected using structured questionnaires through face-to-face interview. Blood grouping and indirect antihuman globulin tests were performed. The relationship between red cell alloimmunization and the independent variables was determined using the chi-square test. P-value <0.05 was considered statistical significance.

Results

In this study, the blood group distributions among the participants were as follows: O, 177 (41.9%); A, 124 (29.4%); B, 76 (18%); and AB, 45 (3.86%). Among the pregnant women included in the study, a total of 51 (12.08%) were identified as RhD-negative. Out of these RhD-negative women, 5 (9.8%) were found to have developed alloimmunization with red blood cell antigens. Miscarriage and post-partum hemorrhage were found to be important factors associated with the occurrence of red cell alloimmunization in these women.

Conclusion

This study showed that one out of ten pregnant women was alloimmunized. Therefore, antenatal blood grouping and indirect antihuman globulin screening should be performed routinely to manage and minimize the undesirable outcomes of alloimmunization during pregnancy.