Supplementary Material for: Fetal anemia: Determinants and perinatal outcomes according to the method of intrauterine blood transfusion

Introduction: Fetal anemia from hemolytic disease treated by intrauterine transfusion (IUT) can be performed by intraperitoneal, intracardiac and intravascular transfusion (IVT). Objective of our study was to compare different transfusion techniques. Methods: Retrospective review of IUT secondary to red cell alloimmunization at eight international centers from 2012-2020. Severe anemia suspected if middle cerebral artery peak systolic velocity  1.5 MoM. Demographic, delivery and postnatal variables were analyzed. Results: Total of 344 procedures, 325 IVT and 19 other techniques (non-IVT) included. No difference in demographics, history of stillbirth (20.5 vs 15.8%, p=0.7), prior pregnancy IUT (25.6 vs 31.6%, p=0.5) or neonatal transfusion (36.1 vs 43.8%, p=0.5). At first IUT, non-IVT had higher hydrops (42.1% vs. 20.4%, p=0.03), lower starting hematocrit (13.3% (±6) vs. 17.7% (±8.2), p = 0.04) and trend towards lower gestational age (24.6 (20.1-27) vs. 26.4 (23.2-29.6) weeks, p=0.08). No difference in birthweight, neonatal phototherapy, exchange or simple transfusion. Conclusion: This is one of the largest studies comparing techniques to treat fetal anemia. IVT was most performed, other techniques were more likely performed in hydrops and lower starting hematocrit was seen. Neither technique affected outcomes. This study may suggest that physician’s experience may be the strongest contributor of outcomes.