Title: Effect of multiple maternal red cell alloantibodies on the occurrence and severity of Hemolytic Disease of the Fetus and Newborn

Introduction: Antenatal antibody screening in India is focused on the detection of anti-D in RhD-negative mothers. HDFN outcome can also be affected by the presence of antibodies other than anti-D. We planned this study to find the impact of ?anti-D in combination with additional antibodies? on the development and severity of HDFN compared with ?anti-D alone?. Methods: This is a retrospective study performed at a referral center in northern India from October 2015 to March 2018. Antibody screening was performed on women with complicated obstetric history. Women with antiD antibody were included in the study and categorized on the basis of presence of additional antibody (anti-D alone or in combination with other antibody). Various clinical, laboratory & interventional parameters were used to define HDFN and severe HDFN. Perinatal outcome was then compared between the two groups. Results: A total of 176 women with anti-D antibody were included in the study. Of these, 136 cases (77.3%) had anti-D alone while at least one additional antibody was present in 40 (22.7 %) cases. Most common additional antibodies were anti-C, anti-E and anti-c. After excluding 46 women for various reasons, 130 women were left for final analysis. Approximately 57% and 78% of cases were affected by severe HDFN amongst women with anti-D alone and in combination, respectively. Relative risk of developing severe HDFN was 1.7 times higher in women with additional antibody. Conclusions: Patients with combination antibodies were found to have more severe HDFN compared to the ones with anti-D alone.