Table 1. Design, characteristics and setting of the included RCTs.

	Overalln=146	MICn=28	HICn=118		RCTsup to 2016n=93	RCTs after 2016n=53
	n (%)	n (%)	n (%)	P value	n (%)	n (%)	P value
RCT design
Parallel RCTs	136 (93.2)	25 (89.3)	111 (94.1)	0.405	91 (97.8)	45 (84.9)	0.005
Parallel cluster RCTs	9 (6.2)	3 (10.7)	6 (5.1)	0.374	1 (1.1)	8 (15.1)	0.001
Crossover RCTs	1 (0.7)	0 (0)	1 (0.8)	>0.999	1 (1.1)	0 (0)	>0.99
Other characteristics of RCTs
Long-term extension RCTs	27 (18.5)	0 (0)	27 (22.9)	0.002	21 (22.6)	6 (11.3)	0.092
Self-identified as ‘pilot’ RCTs	9 (6.2)	1 (3.6)	8 (6.8)	>0.999	5 (5.4)	4 (7.5)	0.724
Secondary publication of RCTs	7 (4.8)	0 (0)	7 (5.9)	>0.999	4 (4.3)	3 (7.5)	0.705
Interventions both in hospital and after discharge	61 (41.8)	7 (25.0)	54 (45.8)	0.074	47 (50.5)	14 (26.4)	0.008
Setting
Type of ward
Only NICU	144 (98.6)	27 (96.4)	117 (99.1)	0.977	93 (100)	51 (96.2)	0.876
NICU and maternity ward	2 (1.4)	1 (3.6)	1 (0.8)	0.348	0 (0.0)	2 (3.8)	0.130
Number of NICUs involved
1	91 (62.3)	19 (67.9)	72 (61)	0.502	57 (61.3)	34 (64.1)	0.732
2	26 (17.8)	6 (21.4)	20 (16.9)	0.578	19 (20.4)	7 (13.2)	0.248
≥3	21 (14.4)	2 (7.1)	19 (16.1)	0.368	12 (12.9)	9 (17.0)	0.500
Not specified	8 (5.5)	1 (3.6)	7 (5.9)	>0.999	5 (5.4)	3 (5.7)	>0.99
World Bank country classification by income level
High-income country	118 (80.8)	0 (0)	118 (100)	–	87 (93.5)	31 (58.5)	<0.001
Upper middle-income country	9 (6.2)	19 (67.9)	0 (0)	–	1 (1.1)	8 (15.1)	0.001
Lower middle-income country	19 (13)	9 (32.1)	0 (0)	–	5 (5.4)	14 (26.4)	0.001
Low-income country	0 (0)	0 (0)	0 (0)	–	0 (0)	0 (0)	–
Multicountry RCTs	2 (1.4)	0 (0)	2 (1.7)	>0.999	0 (0)	2 (3.8)	0.130

p-value < 0.05 in bold.

HIC, high income countries; MIC, upper-middle income countries; NICU, neonatal intensive care unit; RCTs, randomised controlled trials.