Table 3. Univariate analysis of risk factors for overall and severe retinopathy of prematurity.

Risk Factors	Overall ROP incidence		Severe ROP incidence
	RR (95%CI)	P	RR (95%CI)	P
Gestational age	0.747 (0.684 to 0.816)	<0.001	0.804 (0.655 to 0.987)	0.038
Mother age	0.984 (0.942 to 1.028)	0.470	1.040 (0.964 to 1.121)	0.314
Birth weight	0.857 (0.826 to 0.889)	<0.001	0.844 (0.767 to 0.929)	<0.001
Bilirubin (Maximum)	0.948 (0.846 to 1.062)	0.356	0.867 (0.691 to 1.087)	0.215
NICU admission (d)	1.023 (1.014 to 1.031)	<0.001	1.017 (1.002 to 1.032)	0.024
Apgar score	0.791 (0.700 to 0.893)	<0.001	0.742 (0.600 to 0.919)	0.006
Platelet volume	1.139 (0.797 to 1.629)	0.475	0.927 (0.569 to 1.509)	0.760
Platelet count	1.000 (0.997 to 1.002)	0.816	0.999 (0.996 to 1.003)	0.737
IGF-1	0.999 (0.992 to 1.005)	0.714	1.002 (0.984 to 1.020)	0.869
Blood transfusion	4.073 (2.323 to 7.142)	<0.001	6.902 (0.930 to 1.204)	0.059
Surfactant	3.548 (2.043 to 6.159)	<0.001	N/A	<0.001
ARDS	4.964 (1.995 to 2.354)	<0.001	N/A	<0.001
Sepsis	1.966 (1.203 to 3.213)	0.007	2.050 (0.899 to 4.675)	0.088
Gender	0.962 (0.689 to 1.343)	0.820	1.060 (0.594 to 1.890)	0.844
IVH	2.106 (1.031 to 4.303)	0.041	1.500 (0.538 to 4.183)	0.438
GDM	0.692 (0.305 to 1.570)	0.379	2.032 (0.729 to 5.666)	0.175
Pre-eclampsia, eclampsia or HELLP syndrome	1.402 (0.950 to 2.070)	0.088	1.891 (1.046 to 3.418)	0.035
PDA	2.183 (1.517 to 3.141)	<0.001	2.910 (1.624 to 5.212)	<0.001
Cesarean section	0.808 (0.519 to 1.258)	0.345	1.019 (0.474 to 2.192)	0.962
Multiple gestation	1.161 (0.821 to 1.643)	0.398	0.770 (0.411 to 1.443)	0.415

ROP: Retinopathy of prematurity; RR: Relative risk; CI: Confidence interval; IGF-1: Insulin-like growth factor-1; ARDS: Acute respiratory distress syndrome; IVH: Intraventricular hemorrhage; GDM: Gestational diabetes mellitus; PDA: Patent ductus arteriosus; N/A: Not available due to no observation in one of the levels.