RETNLB and necrotizing enterocolitis: The concentration of serum Relmβ > 19.7 μmol/L has a moderate value in the surgery-decision making of NEC when considered in isolation; a predictive model combining abdominal wall tenseness, abdominal tenderness and Relmβ > 19.7 μmol/L showed high predictive value when the score was ≥2 points.