To Örebro University

Leukocytosis, namely a markedly elevated white blood cell (WBC) count, occurs in 1.3–17.0% of infants admitted to neonatal intensive care units and can be induced by infection, inflammation, stress or medication. Postnatal leukocytosis can also reflect immature granulocytopoiesis in the bone marrow or systemic fetal inflammatory response syndrome, which particularly affects preterm infants (1). Chorioamnionitis and neonatal morbidities, such as sepsis, necrotising enterocolitis, intraventricular hemorrhage, prolonged oxygen support and bronchopulmonary dysplasia, have been associated with leukocytosis in preterm infants (2).