Inflammatory cells in the lungs of premature infants on the first day of life: perinatal risk factors and origin of cells.

Neither the origin of leucocytes in the premature newborn airway nor their relationship to perinatal factors has been adequately determined. In order to sample airway cells, modified bronchoalveolar lavage was performed on 74 intubated infants of < 32 weeks' gestation and < 24 hours of age. Cells were counted, stained and, in a small separate group of six infants, four boys and two girls, probed for the Y chromosome with suitable control samples. Perinatal risk factors for increased airway cellularity were analysed by multiple regression. Premature rupture of membranes of more than 24 hours' duration was independently associated with increased numbers of airway leucocytes (n = 74). More than 90% of airway leucocytes from four boys with pulmonary inflammation were positive for the Y chromosome indicating that the cells were of fetal rather than maternal origin.