A systematic review with a meta-analysis of eleven observational studies evaluated whether PRBC transfusions were associated with an increased risk of NEC in the 48 hours following the transfusion. Most of these studies had a low or moderate risk of bias. One study actually found a lower incidence of NEC after transfusion, but most of the other studies found the opposite. The meta-analysis showed a higher odds ratio for NEC after recent transfusion. Infants who developed NEC following transfusion had a lower gestational age, lower birth weight, higher odds of PDA, and higher odds of being ventilated than those who developed NEC unrelated to transfusion. They also had a higher mortality. Two studies reported that after unit practice was changed to withholding feedings during PRBC transfusion, the frequency of NEC decreased in those units.