Fig. 5.

Plausible explanation for late mortality in oxygen saturation trials in preterm infants. The increased mortality observed in extremely preterm infants randomized to the 85%–89% SpO₂ arm of the Neonatal Oxygenation Prospective Meta-Analysis (NeOProM) trials occurs after the first 2 weeks of postnatal life. Vento et al. (2012) have speculated that a gradual postnatal decrease in hemoglobin (especially if threshold for transfusion is low in the neonatal intensive care unit and hemoglobin gradually decreases with time) results in decreased CaO₂, which may lead to an oxygen delivery below the critical point (dashed line), as shown in Fig. 4. Suboptimal oxygen delivery can potentially result in necrotizing enterocolitis and mortality, as has been observed in the low saturation target group of the NeOProM trials.