Supplementary Material for: Prevalence of Alloimmunization and Associated Risk Factors Among Antenatal Women in India: A Systematic Review and Meta-Analysis

Background
Maternal alloimmunization can lead to significant perinatal morbidity and mortality. The rate of maternal alloimmunization reported is varied across the studies conducted in India. A systematic review will help in understanding the overall prevalence of alloimmunization. Additionally, the study aimed at understanding the factors affecting the rate of maternal alloimmunization.
Methods
A search of original articles reporting rate of alloimmunization among antenatal women published in English language from India was performed in SCOPUS, GOOGLE SCHOLAR, MEDLINE, CINAHL databases. Two independent teams, each comprising two reviewers, extracted data from the eligible studies. Meta-analysis was performed for cumulative estimates by binary random effects model using the restricted maximum likelihood method.
Results
Fourteen studies published between 2011 and 2023 were included. The pooled prevalence of maternal alloimmunization was 2.0 per 100 (95% CI: 1.5–2.5) among antenatal women, with significant heterogeneity across studies. Anti-D was the most frequently identified antibody (56.39%), followed by anti-D + anti-C (10.68%) and anti-E (5.71%). Higher odds of alloimmunization were observed in women with RhD-negative blood group, multigravida status, history of blood transfusion, and bad obstetric history.
Conclusion
Despite the availability of anti-D prophylaxis, over half of the alloimmunized women developed anti-D antibodies, indicating potential gaps in prevention strategies. Further research is needed to understand these gaps and implement effective interventions to minimize this preventable cause of fetal and neonatal complications. Prophylactic antigen-matched (Rh and Kell) red cell transfusion in girls and women of reproductive age may reduce the burden of alloimmunization.