Table 1

Infant characteristics, growth and morbidity by gestational age at birth

	Gestational age at birth (weeks)
	23		24		25		26		27		28		29		30		All
	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	N	Per cent
Infants	117	4.6	314	12.5	399	15.8	482	19.1	249	9.9	296	11.7	323	12.8	341	13.5	2521	100
Female sex	58	49.6	137	43.6	190	47.6	229	47.5	119	47.8	139	47.0	134	41.5	162	47.5	1168	46.3
Country
NA*	53	45.3	168	53.5	190	47.6	227	47.1	237	95.2	277	93.6	299	92.6	319	93.5	1770	70.2
Sweden	64	54.7	146	46.5	209	52.4	255	52.9	12	4.8	19	6.4	24	7.4	22	6.4	751	29.8
SGA	5	4.3	38	12.1	81	20.3	115	23.9	77	30.9	110	37.2	107	33.1	114	33.4	647	25.7
	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR	Mdn	IQR
BW (g)	595	550–655	675	610–735	770	693–858	890	776–995	989	865–1080	1071	921–1211	1287	1100–1420	1415	1195–1550	915	731–1153
BWSDS (SDS)	−0.4	−1.0–0.4	−0.6	−1.4–0.0	−1.0	−1.7–0.1	−1.0	−2.0–0.2	−1.3	−2.3–0.6	−1.6	−2.6–0.8	−1.3	−2.3–0.4	−1.4	−2.5–0.6	−1.1	−2.0–0.3
Weight at 36 weeks PMA (g)	2072	1847–2263	2123	1932–2319	2126	1881–2377	2190	1905–2415	2244	1922–2501	2179	1958–2500	2320	1973–2582	2206	1902–2506	2157	1909–2391
WSDS at 36 weeks PMA (SDS)	−2.3	−2.9–1.8	−2.2	−2.8–1.6	−2.2	−2.9–1.4	−2.0	−2.9–1.2	−1.6	−2.7–0.8	−1.9	−2.5–0.9	−1.5	−2.6–0.7	−1.8	−2.9–0.9	−1.9	−2.7–1.2
Growth rate† (g/kg/d)	13.7	12.6–15.2	13.8	12.6–15.2	13.8	12.7–15.4	13.8	12.3–15.4	13.7	12.3–15.2	13.3	11.6–14.9	12.4	11.0–14.2	11.8	9.8–13.9	13.3	11.8–15.0
MAX rate (g/kg/d)	18.9	11.5–23.6	18.3	12.2–23.8	19.7	13.1–25.6	20.3	13.4–25.6	21.7	17.8–25.1	20.5	16.9–23.8	20.4	16.6–23.7	19.0	15.7–22.7	17.7	11.3–22.7
PMA @MAX	30		30		30		30		31		32		33		34		31
	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	n	Per cent	N	Per cent
ROP‡
No	9	7.7	17	5.4	69	17.3	166	34.4	99	39.8	185	62.5	236	73.1	304	89.1	1085	43.0
ROP 1–2	40	34.2	131	41.9	215	54.0	236	49.0	127	51.0	98	33.1	84	26.0	34	10.0	965	38.3
ROP≥3	68	58.1	165	52.7	114	28.6	80	16.6	23	9.2	13	4.4	3	0.9	3	0.9	471	18.7
Trt	51	43.6	109	34.9	65	16.3	39	8.1	16	6.4	5	1.7	3	0.9	0	0.0	288	11.4
BPD‡	104	88.9	247	79.2	289	72.8	308	64.6	124	49.8	108	36.5	58	18.0	30	8.8	1268	50.5
NEC	9	7.7	47	15.0	33	8.3	42	8.7	25	10.0	32	10.8	27	8.4	15	4.4	230	9.1
All IVH	60	51.3	144	45.9	141	35.3	118	24.5	65	26.1	56	18.9	64	19.8	44	12.9	692	27.4

*North America (USA and Canada).
†Overall growth rate from birth to 36 weeks PMA calculated for 2344 infants.
‡Information regarding ROP was missing for one infant born at a gestational age of 24 weeks, and one infant at 25 weeks. Information regarding BPD was missing from two infants born at a gestational age of 24 weeks, two infants at 25 weeks and five infants born at 26 weeks.
BWSDS, birth weight SD score; BPD, bronchopulmonary dysplasia; IVH, intraventricular haemorrhage; Mdn, median; NEC, necrotising enterocolitis; PMA, postmenstrual age; ROP, retinopathy of prematurity; Trt, treatment for ROP; w, weeks. IQR (25th to 75th centile).