TABLE 4.

Data from the EXPRESS (Sweden, 2004–06), EPICure‐2 (England, 2006) and EPIPAGE‐2 (France, 2011) cohorts for babies who were discharged alive from hospital

Variable Levels	EXPRESS		EPICure‐2		EPIPAGE‐2		p‐value
	n	%	n	%	n	%
Gestational age at delivery (weeks)
23	58	11.7	69	6.6	1	0.2	<0.001
24	95	19.1	178	17.1	58	10.5
25	164	33	345	33.2	181	32.8
26	180	36.2	448	43.1	311	56.4
Sex
Male	270	54.3	505	48.6	280	50.8	0.105
Female	227	45.7	535	51.4	271	49.2
Birth weight (g)
<500 g	18	3.6	12	1.2	4	0.7	<0.001
≥500 g	479	96.4	1028	98.8	547	99.3
Congenital anomalies
No	442	88.9	1004	98.9	545	98.9	<0.001
Yes	55	11.1	11	1.1	6	1.1
Missing	0	–	25	–	0	–
Highest grade of IVH
0	310	62.9	490	47.3	286	51.9	<0.001
1	89	18.1	170	16.4	93	16.9
2	45	9.1	188	18.2	126	22.9
3	26	5.3	54	5.2	29	5.3
4	23	4.7	133	12.9	17	3.1
Missing	4	–	5	–	0	–
Cystic PVL
No	469	94.4	976	94.3	538	97.6	0.008
Yes	28	5.6	59	5.7	13	2.4
Missing	0	–	5	–	0	–
PDA treated surgically
No	362	72.8	867	83.9	406	76.0	<0.001
Yes	135	27.2	166	16.1	128	24.0
Missing	0	–	7	–	17	–
NEC treated surgically
No	476	96.9	961	92.4	526	95.5	<0.001
Yes	15	3.1	79	7.6	25	4.5
Missing	6	–	0	–	0	–
Bronchopulmonary dysplasia
None/mild	142	31.3	323	31.1	304	60.8	<0.001
Moderate	199	43.9	291	28.0	64	12.8
Severe	112	24.7	425	40.9	132	26.4
Missing	44	–	1	–	51	–
Treated ROP
No	124	52.5	474	74.1	330	94.0	<0.001
Yes	112	47.5	166	25.9	21	6.0
Missing	261	–	400	–	200	–
ROP stage
0	137	27.8	393	38.0	186	52.2	<0.001
1	75	15.2	198	19.2	77	21.6
2	112	22.8	229	22.2	65	18.3
3	162	32.9	209	20.2	27	7.6
4	3	0.6	3	0.3	1	0.3
5	3	0.6	1	0.1	0	0.0
Missing	5	–	7	–	195	–
Total number of neonatal morbidities
0	231	46.5	410	39.4	348	63.2	<0.001
1	180	36.2	373	35.9	165	29.9
2	68	13.7	188	18.1	35	6.4
3	16	3.2	62	6.0	3	0.5
4	2	0.4	7	0.7	0	0.0
Missing	0	–	0	–	0	–

Total neonatal morbidities: IVH ≥ grade III, PVL, surgically treated NEC, ROP ≥ stage 3, severe bronchopulmonary dysplasia.

Abbreviations: IVH, intraventricular haemorrhage; NEC, necrotising enterocolitis; PDA, patent ductus arteriosus; PVL, periventricular leukomalacia; ROP, retinopathy of prematurity.