MUC1 and Sepsis: Plasma KL-6 levels were not significantly correlated with gestational age (at 7 days: r = −0.202, P = 0.085; at 14 days: r = −0.084, P = 0.478) (Table 2) but showed a significant correlation with birth weight (at 7 days: r = −0.452, P < 0.001; at 14 days: r = −0.424, P < 0.001) (Table 2), sepsis (at 7 days: P = 0.01; at 14 days: P = 0.05) (Figure 2), and mechanical ventilation ≥1 week (at 7 days: P < 0.0001; at 14 days: P < 0.0001) (Figure 3).