The relationship between leukemoid reaction and perinatal morbidity, mortality, and chorioamnionitis in low birth weight infants.

Objectives: Neonatal leukemoid reaction (NLR) is relatively rare and considered as a white blood cell (WBC) count ≥50×10(9)/l . The aim of this study was to investigate the association of NLR with neonatal morbidity and mortality and maternal chorioamnionitis in low birth weight infants.

Methods: In this case-controlled retrospective study, the medical records of 1200 newborn infants with a birth weight <2500g admitted to the neonatal unit over a period of 5 years were reviewed. The infants who developed features of NLR (n=17, 1.4%) formed the study group, while the remainder without NLR, matched for gestational age and birth weight (n=123), formed the control group. A chart review was performed and salient demographic, clinical, and laboratory data abstracted. A statistical analysis was subsequently performed on this data.

Results: The mean WBC and absolute neutrophil counts of infants with NLR were significantly higher than those in the control group. The peak time of NLR was at 7.9±3.6 (interquartile range (IQR) 1-30) days and on average it improved within 4.1±1.95 (IQR 2-9) days. It was noted that those infants with NLR were mostly born by vaginal delivery and their mothers had a higher rate of early rupture of the membranes and chorioamnionitis. NLR was associated with a 4-fold increase in sepsis, 20-fold increase in intraventricular hemorrhage, 54-fold increase in bronchopulmonary dysplasia, and 6-fold increase in mortality. In the study group, those infants whose mothers had chorioamnionitis had a higher rate of early rupture of the membranes and they developed sepsis and intraventricular hemorrhage more often than those whose mothers did not have clinical chorioamnionitis.

Conclusions: In low birth weight newborn infants, NLR is significantly associated with sepsis, intraventricular hemorrhage, bronchopulmonary dysplasia, and a high mortality rate. Also, those infants with NLR are more likely to be born to mothers with chorioamnionitis and they face sepsis and intraventricular hemorrhage more often.