Premature infants exposed to chorioamnionitis are at increased risk for periventricular leukomalacia (PVL) and intraventricular hemorrhage (IVH), lesions that may result from inflammation and/or fluctuations in cerebral blood flow. The effect of chorioamnionitis on near-infrared spectroscopy (NIRS) measures of cerebral oxygen delivery has not been evaluated previously. Forty-nine infants born at 25-31 6/7 wk gestation underwent NIRS examination on d 1, 2, 3, and 7 of life. Variability in NIRS tracings was analyzed by partitioning each tracing into three components: long-term, intermediate, and short-term variability; the latter two components were analyzed. Chorioamnionitis-exposed infants manifest reduced intermediate variability in cerebral oxygenated and deoxygenated Hb but not total Hb. Infants with severe IVH/PVL had the lowest intermediate variability on d 1. Short-term variability was similar between chorioamnionitis-exposed and unexposed infants, and between infants with versus without severe IVH or PVL. We conclude that intermediate-term variability in NIRS cerebral oxygen delivery is reduced in chorioamnionitis-exposed infants. We speculate that intermediate variability represents the important time frame for evaluating the pathogenesis of perinatal brain injury. Further studies are needed to determine how these findings relate to cerebral blood flow autoregulation and oxygen utilization in premature infants. C horioamnionitis is perhaps the most common cause of premature delivery. Recent epidemiologic and clinical investigations indicate that premature infants who are exposed to chorioamnionitis are at increased risk for developing IVH (1), PVL (1,2), and cerebral palsy (2-4). The etiology of the white matter injury in chorioamnionitis-exposed infants remains uncertain but likely involves some component of ischemic (5-8) and/or inflammatory (9,10) damage to the developing oligodendroglia. It has been demonstrated that preterm infants who develop IVH have fluctuations in Doppler-derived cerebral blood flow velocities (11). With the application of NIRS, it became evident that infants with both IVH and PVL have fluctuations in cerebral oxygen delivery (12) that correlate with fluctuations in blood pressure and indicate impaired cerebral autoregulatory ability (11). The relationship between variability in NIRS measures of cerebral oxygen delivery and exposure to chorioamnionitis has not been evaluated previously.The overall objective of this investigation was to determine the variability among NIRS measures of cerebral oxygen delivery in premature infants exposed and unexposed to chorioamnionitis. We first devised a method that would allow us to assess both intermediate and short-term variability in NIRS measures of cerebral oxygenated, deoxygenated, and total Hb. Next, we tested the hypothesis that variability decreases with increasing gestational and postnatal age, as the risk of IVH and PVL abate. Finally, we compared variability in NIRS measures of cerebral oxygen delivery between infants ex...