Table 2.

Risk factors for BPD based on stepwise multiple logistic regression analysis.

Variable	β	S.E	χ2	P	OR	95%CI
Electrolyte disturbances	2.400	0.763	9.899	0.002	11.024	2.472–49.167
hs-PDA	3.351	1.378	5.912	0.015	28.530	1.915–425.039
The age that infants achieved 120 kcal/kg.d via enteral feeding ≥40 days after birth	2.871	0.749	14.707	0.000	17.652	2.472–49.167

Electrolyte disturbance includes hyponatremia, hypernatremia, hypokalemia, hyperkalemia, hypocalcemia, hypercalcemia, hypochloridemia, and hyperchloremia. hs-PDA refers to confirming the opening of the ductus arteriosus (DA) by echocardiography. And there is a significant change in hemodynamics.