Table 1. Random effects meta-analyses of potential confounders.

Meta-analysis	Chorioamnionitis	k	Effect size	95% CI	Z	P	Heterogeneity
							Q	P	I2
Gestational age (weeks)	Clinical	4	MD -1.151	−1.612 to −0.689	−4.888	<0.001	25.308	<0.001	88.146
	Histological	29	MD -1.418	−1.725 to −1.112	−9.070	<0.001	333.271	<0.001	91.958
	Any type	33	MD -1.336	−1.592 to −1.081	−10.260	<0.001	369.827	<0.001	91.347
Birth weight (g)	Clinical	4	MD -48	−130 to 34	−1.145	0.252	37.199	<0.001	91.935
	Histological	28	MD -80	−113 to −46	−4.659	<0.001	107.816	<0.001	74.957
	Any type	32	MD -75	−106 to −44	−4.745	<0.001	147.878	<0.001	79.037
Antenatal corticosteroids	Clinical	3	OR 1.498	1.024 to 2.191	−1.504	0.133	11.743	0.003	82.969
	Histological	26	OR 1.234	1.049 to 1.451	−4.549	<0.001	60.735	<0.001	58.837
	Any type	29	OR 1.271	1.095 to 1.475	3.156	0.002	72.503	<0.001	61.381
Cesarean section	Clinical	3	OR 0.434	0.389 to 0.485	−14.725	<0.001	1.695	0.428	0.000
	Histological	17	OR 0.373	0.297 to 0.469	−8.483	<0.001	83.466	<0.001	80.830
	Any type	20	OR 0.422	0.382 to 0.466	−16.953	<0.001	85.911	<0.001	77.884
PROM	Any type	16	OR 2.884	2.085 to 3.989	6.401	<0.001	107.419	<0.001	86.036
SGA	Any type	11	OR 0.341	0.211 to 0.549	4.423	<0.001	58.549	<0.001	82.920
Preeclampsia	Any type	6	OR 0.143	0.084 to 0.243	−7.182	<0.001	13.948	0.016	64.153

K: number of studies; PDA: patent ductus arteriosus; MD: mean difference (chorioamnionitis-exposed minus unexposed); OR: odds ratio (OR > 1 means increased risk in infants exposed to chorioamnionitis);; PROM: premature rupture of membranes; SGA: small for gestational age.