PERIPHERAL LEUKOCYTE COUNT AND LEUKOCYTE INDEXES IN HEALTHY NEWBORN TERM INFANTS

Purpose: This study was designed to determine normal values for the pe ripheral leukocyte count and leukocyte indexes in healthy term neonate s at a specific time after birth. Methods: We prospectively enrolled 1 93 healthy term-gestation neonates with no identifiable perinatal risk factors for sepsis. At 4 hours of age a blood sample was collected by warmed heel stick. An automated Coulter complete blood cell count and a 100-cell manual differential leukocyte count were performed on each sample. The differential count was performed by a single hematopathol ogist unaware of the clinical status of each infant. Perinatal factors were identified by review of the mothers' and infants' hospital recor ds. Results: The mean ratio of immature to total neutrophils was 0.16 (SD 0.10), and the 10% to 90% range was 0.05 to 0.27. The mean leukocy te count was 24.06 X 10(9)/L. (24,060/mm(3)), and the 10% to 90% range was 16.2 to 31.5 X 10(9)/L. (16,200 to 31,500/mm(3)). Neutropenia, <1 .5 x 10(9)/L (1500/mm(3)) segmented plus band form neutrophils, was no t observed. Of all the perinatal factors studied, only the duration of stage 1 labor was found to be associated with significant elevations in the leukocyte and absolute neutrophil counts. Conclusions: Previous ly published normal ranges for leukocyte indexes in healthy newborn in fants during the early neonatal period are too restrictive; reference standards should be broadened.