ABO Incongruency Increases Risk for Necrotizing Enterocolitis in Preterm Neonates

Introduction: Preterm neonates are at high risk for complications, and inflammation has been implicated in many of these pathologies. ABO incongruency occurs when the maternal and neonatal blood types are different and may cause complications when the mother creates antibodies against neonatal blood type antigens. In this study, we investigated whether preterm neonates with type A or B blood born to mothers with type O blood (ABO incongruent) had higher rates of neonatal complications than neonates with type O blood born to mothers with type O blood (ABO congruent). We hypothesized that preterm neonates who were ABO incongruent would have a higher incidence of neonatal morbidity. Methods: This was a population-based single-center retrospective cohort study of 371 preterm neonates whose mothers had O blood type, were born between 21 0/7 and 32 6/7 weeks gestation, and admitted to University of Iowa Health Care Neonatal Intensive Care Unit between January 2018 and December 2022. Neonates were grouped by ABO incongruent versus congruent as well as by gestational age (GA) (22-26 and 27-32 weeks GA). Demographics data were collected. Outcomes included bronchopulmonary dysplasia (BPD), pulmonary hypertension, patent ductus arteriosus (PDA), necrotizing enterocolitis (NEC), packed red blood cell (pRBC) transfusions, intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), and survival to discharge. Results: ABO incongruent neonates between 27-32 weeks GA were more likely to have NEC and had a trend towards an increased incidence of early pulmonary hypertension. There were trends towards more heart dysfunction and severity of IVH in neonates between 22-26 weeks GA. Conclusion: ABO incongruency is associated with neonatal complications in the preterm population. This study is underpowered to adequately evaluate all neonatal morbidities. More studies are required to evaluate the effects of ABO incongruency on neonatal outcomes, particularly on NEC and pulmonary hypertension.