Background: Hemolytic disease of the newborn (HDN) is a less recognized cause of neonatal neutropenia. Therefore, this study aims to estimate the incidence of neutropenia and identify associated factors in infants with HDN at a tertiary care center. 

Methods: This retrospective cohort study included infants with HDN who presented at a tertiary care center in Saudi Arabia between March 2008 and September 2023. Neutropenia was defined as an absolute neutrophil count of less than 1.5mL. Results: Among 339 neonates with HDN, 50.1% were male, and 49.9% were female. Rh isoimmunization was the most common antibody type, observed in 58.7% of cases. The severity of HDN was classified as mild in 62.6% of neonates, moderate in 33.3%, and severe in 4.1%. Neutropenia was more prevalent in moderate-to-severe HDN cases (P=0.047). The incidence rate of neutropenia was 4.1 per 1,000 persondays, with 7.4% of neonates (25/339) being neutropenic at birth. Among these, 17 out of 25 neonates showed resolution within 2 days. Multivariate analysis identified male gender (P=0.022), low gestational age (P=0.008), low birth weight (P= 0.039), and the need for exchange transfusion (P=0.036) as significant risk factors for neutropenia. 

Conclusion: Neutropenia in infants with HDN, irrespective of antibody type, is generally a benign, self-limiting condition. This condition predominantly affects male neonates with moderate-to-severe HDN and prematurity and can be managed conservatively.

Fawzah Alrwuili is a consultant in general pediatrics and chronic complex care at McMaster University, Canada. She works at the King Faisal Specialist Hospital and Research Center in Riyadh and is interested in outpatient care for high-risk neonates. Additionally, she serves as the director for the Advanced General Pediatric Fellowship.