Objectives: To characterize the time course of changes in neutrophil counts, and to draw comparisons across four gestational age groups with respect to incidence of neutropenia and neutrophilia over the first months of life in a single center.
Study design: Weekly complete blood counts (CBC) were collected on all NICU patients. Changes in neutrophil counts over time were examined, the incidence of neutropenia (< or =1100/mm3) and neutrophilia (> or =15,000/mm3 before, and > or =6000/mm3 after 60 hours of life) were determined, and clinical correlations sought.
Results: A total of 2038 CBCs from 347 infants were evaluated. Changes in neonatal neutrophil counts were associated with gestational age, postnatal age, pregnancy-induced hypertension (PIH), and infection, either presumed or documented. Overall, neutropenia occurred 91 times in 50 infants (14% of infants), and the prevalence decreased with maturity and increased with exposure to PIH. In the first week of life, 69% of the neutropenia occurred in infants exposed to PIH. Neutrophilia occurred 579 times in 146 infants (42% of infants), and the prevalence decreased with maturity. Neutrophil deviations from the normal range were often asymptomatic and not associated with recognized clinical conditions.
Conclusions: The incidence and prevalence of neutrophil abnormalities increased with immaturity, and were more common than previously appreciated in hospitalized preterm infants.