Comparison 1. Delayed versus early introduction of progressive enteral feeding (all trials).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Necrotising enterocolitis (NEC)	13	1507	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.58, 1.14]
1.1.1 Human milk or formula‐fed (or mixed) infants	9	1313	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.59, 1.24]
1.1.2 Only human milk‐fed infants	3	156	Risk Ratio (M‐H, Fixed, 95% CI)	0.22 [0.04, 1.28]
1.1.3 Only formula‐fed infants	1	38	Risk Ratio (M‐H, Fixed, 95% CI)	1.08 [0.40, 2.94]
1.2 NEC (subgroup analysis of infants growth‐restricted or with AREDFV)	13	1507	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.58, 1.14]
1.2.1 Trials including only growth‐restricted/AREDFV infants	6	767	Risk Ratio (M‐H, Fixed, 95% CI)	0.83 [0.52, 1.32]
1.2.2 Trials including all infants	7	740	Risk Ratio (M‐H, Fixed, 95% CI)	0.79 [0.48, 1.30]
1.3 Mortality prior to discharge	12	1399	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.70, 1.36]
1.3.1 Human milk or formula‐fed (or mixed) infants	9	1267	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.59, 1.27]
1.3.2 Only human milk‐fed infants	2	94	Risk Ratio (M‐H, Fixed, 95% CI)	1.75 [0.55, 5.57]
1.3.3 Only formula‐fed infants	1	38	Risk Ratio (M‐H, Fixed, 95% CI)	1.44 [0.57, 3.61]
1.4 Mortality (subgroup analysis of infants growth‐restricted or with AREDFV)	12	1399	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.70, 1.36]
1.4.1 Trials including only growth‐restricted/AREDFV infants	5	642	Risk Ratio (M‐H, Fixed, 95% CI)	1.20 [0.68, 2.12]
1.4.2 Trials including all infants	7	757	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.57, 1.31]
1.5 Feed intolerance	6	581	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.68, 0.97]
1.5.1 Human milk or formula‐fed (or mixed) infants	4	487	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.72, 1.02]
1.5.2 Only human milk‐fed infants	2	94	Risk Ratio (M‐H, Fixed, 95% CI)	0.55 [0.30, 1.01]
1.6 Invasive infection	7	872	Risk Ratio (M‐H, Fixed, 95% CI)	1.44 [1.15, 1.80]
1.6.1 Human milk or formula‐fed (or mixed) infants	4	716	Risk Ratio (M‐H, Fixed, 95% CI)	1.33 [1.06, 1.68]
1.6.2 Only human milk‐fed infants	3	156	Risk Ratio (M‐H, Fixed, 95% CI)	2.57 [1.21, 5.46]
1.7 Duration of hospital admission (days)	4	378	Mean Difference (IV, Fixed, 95% CI)	4.57 [1.53, 7.61]
1.7.1 Human milk or formula‐fed (or mixed) infants	3	346	Mean Difference (IV, Fixed, 95% CI)	4.90 [1.62, 8.17]
1.7.2 Only human milk‐fed infants	1	32	Mean Difference (IV, Fixed, 95% CI)	2.50 [‐5.76, 10.76]