Table 7.

 Multivariate ORs with 95% CIs, adjusted for confounders

Model and confounders	Risk factor	OR (95% CI)	p value
Model 1 (maternal UTI, PROM, maternal age, preterm deliverya)	Caesarean section	1.08 (1.02, 1.15)	<0.01
Model 2 (maternal UTI, PROM, maternal age)	Very pretermb	0.54 (0.38, 0.76)	<0.001
	Moderate to late pretermc	1.24 (1.14, 1.35)	<0.001
Model 3 (maternal UTI, PROM, maternal age, preterm deliverya)	Birthweight z score	1.08 (1.06, 1.10)	<0.001
Model 4 (maternal age)	UTI	1.39 (1.04, 1.86)	0.025
Model 5 (maternal age)	PROM	1.08 (1.01, 1.16)	0.023

The confounders are variables that introduced spurious associations through backdoor paths in the directed acyclic graph shown in Fig. 2

^aGestational age at birth <259 days, ^bgestational age at birth <224 days, ^cgestational age at birth 224–258 days; full term ≥259 days is used as reference