Which blade is unsuitable for preterm newborn intubation?

The No. 2 blade is unsuitable for preterm newborn intubation because it is generally too large for their anatomical structure. Preterm newborns typically have smaller and more delicate airways, requiring more appropriately sized blades for intubation that can properly visualize and manage these airways without causing trauma.

In contrast, the No. 00 blade is specifically designed for the very small airways of preterm infants, making it the best choice for this population. The No. 0 and No. 1 blades, while larger than the No. 00, are still used for neonatal intubation, as they can accommodate the size and anatomy of term infants and some preterm infants better than the No. 2 blade. Thus, the No. 2 blade's larger size makes it inappropriate for this specific scenario.