The Transfusion of Prematures (TOP) study is a randomized clinical trial designed to determine whether the primary outcome of death or significant neurodevelopmental impairment (NDI) in survivors at 22 to 26 months is less common among preterm infants maintained at a higher hemoglobin level. This trial provides an opportunity to conduct a secondary study on near-infrared spectroscopy (NIRS), a noninvasive bedside technology able to reliably measure regional tissue oxygenation of both cerebral and mesenteric tissues. RTI International is working to determine whether abnormal cerebral NIRS measures are a better predictor of NDI than hemoglobin alone and whether abnormal mesenteric NIRS measures are associated with the development of NEC within the 48 hours following a transfusion. Additionally, as the data coordinating center for the NIRS study, RTI collaborates with the study's clinical investigators in developing and implementing the study and disseminating results, providing leadership in statistical design and analysis, and providing data management and logistical support.