Table 1.

Row percents of infants classified by their duration of ventilation during the first two weeks within strata defined by perinatal and neonatal characteristics.

Characteristics		Duration of ventilation*			Row N
		< 7 days	7-13 days	14 days
Inflamed placenta	Yes	38	19	43	228
	No	32	21	47	43 8
Sex	Male	31	21	48	375
	Female	38	19	42	351
Number of fetuses	1	33	22	45	470
	2+	35	20	46	256
Gestational age (weeks)	23-24	5	11	83	150
	25-26	29	23	48	340
	27	60	23	17	236
Birth weight (g)	≤ 750	12	15	74	275
	751-1000	42	25	33	316
	> 1000	61	21	17	135
Birth weight Z-score**	< −2	24	13	62	45
	≥ −2, < −1	19	23	59	97
	≥ −1	37	21	42	584
Course of antenatal corticosteroids	Complete	38	21	40	480
	Partial	27	18	55	174
	None	22	21	57	72
Patent ductus arteriosus	Yes	21	22	56	466
	No	57	16	27	259
Surfactant first week	Yes	30	20	50	640
	No	66	21	13	86
Postnatal corticosteroids	Yes	10	28	63	94
	No	38	19	43	632
Bacteremia† first week	Yes	19	30	51	43
	No	35	21	45	682
Bacteremia† second week	Yes	22	31	47	93
	No	36	19	45	630
Maximum number (%)		247 (34)	149 (21)	330 (45)	726

^*Numbers = row percentages

^**Birth weight Z-scores based on Yudkin et al. ¹²

^†Culture positive