Table 6.

Univariate analysis of risk factors of ROP.

	Risk factors	ROP patients	Non-ROP subjects	t	P
Neonatal factors	Gestational age (w)	30.3±2.2	32.0±2.0	t=6.97	<0.001
	Birth weight (g)	1415±305	1660±350	t=6.18	<0.001
	Total days of oxygen supplement (d)*	27.2±21.8	14.3±12.2	t=–5.46	<0.001
	Days of mechanical ventilation (d)	3.6±8.8	1.4±3.5	t=–3.75	<0.001
	Days of non-mechanical ventilation (d)**	23.6±18. 4	12.9±11.3	t=–5.35	<0.001
	Sex (M/F)	50/42	212/155	χ2=0.351	0.554
	Neonatal pneumonia	87	346	χ2=0.011	0.915
	ARDS, apnea, respiratory failure, asphyxia	55	160	χ2=7.739	0.005
	Pulmonary hemorrhage	6	21	χ2=0.085	0.771
	Encephalopathy of preterm infants	78	255	χ2=8.647	0.003
	Sepsis	11	34	χ2=0.603	0.437
	Congenital heart diseases	47	163	χ2=1.320	0.251
	Myocardial injury	55	254	χ2=2.972	0.085
	Coagulation dysfunction	45	179	χ2=0.001	0.981
	Hyperbilirubinemia, pathological jaundice	49	203	χ2=0.125	0.724
	Hypoproteinemia	36	98	χ2=5.496	0.019
	Hypoglycemia	9	39	χ2=0.056	0.813
	Hyperglycemia	16	37	χ2=3.848	0.050
	Anemia	78	255	χ2=8.647	0.003
	Acid-base imbalance	47	167	χ2=0.921	0.337
	Oxygen supplement	90	331	χ2=5.648	0.017
	Mechanical ventilation	29	90	χ2=1.876	0.171
	Blood transfusion	77	206	χ2=23.642	<0.001
	Multiple deliveries	28	123	χ2=2.399	0.494
	Vasoactive substances	57	152	χ2=12.513	<0.001
	Pulmonary surfactant	22	49	χ2=6.275	0.012
	Erythropoietin	15	49	χ2=0.535	0.465
Maternal factors	Maternal age	29.45±5.79	29.11±5.45	t=–0.516	0.606
	Eutocia/Cesarean section	43/49	158/209	χ2=0.406	0.524
	premature rupture of fetal membranes	36	156	χ2=0.001	0.977
	Amniotic fluid abnormalities	5	27	χ2=0.419	0.517
	Fetal distress	10	45	χ2=0.135	0.713
	Placenta praevia	3	32	χ2=3.112	0.078
	Placental abruption	3	10	χ2<0.001	1.000
	Gestational hypertension	7	34	χ2=0.248	0.619
	Gestational cholestasis	5	87	χ2=0.002	0.961
	Gestational diabetes	2	20	χ2=1.086	0.297
	Anemia in pregnancy	5	24	χ2=0.152	0.697
	Cold	25	110	χ2=0.278	0.598
	Dexamethasone	20	101	χ2=1.267	0.26
	Penicillin	1	14	χ2=0.976	0.323
	Tocolytic agents	5	11	χ2=0.676	0.411

^*Total days of oxygen supplementation = days of mechanical ventilation + days of non-mechanical ventilation;

^**Days of non-mechanical ventilation = total days of oxygen supplementation via nasal tube, mask or chamber.

ROP – retinopathy of prematurity; ARDS – Acute Respiratory Distress Syndrome; HIE – hypoxic-ischemic encephalopathy.