Table 8.
Subgroup analyses: 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, maternal BMI) | Caesarean section | 1.04 (0.96, 1.15) | 0.30 |
| Model 2 (maternal UTI, PROM, maternal age, maternal BMI) | Very pretermb | 0.64 (0.37, 0.99) | 0.046 |
| Moderate to late pretermc | 1.22 (1.07, 1.40) | <0.01 | |
| Model 3 (maternal UTI, PROM, maternal age, preterm deliverya, maternal BMI) | Birthweight z score | 1.07 (1.04, 1.10) | <0.001 |
| Model 4 (maternal age) | BMI: overweightd | 1.10 (1.02, 1.19) | <0.01 |
| BMI: obesed | 1.27 (1.15, 1.41) | <0.001 |
The confounders are variables that introduced spurious associations through backdoor paths in the directed acyclic graph shown in Fig. 3
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
dFirst-trimester maternal BMI: overweight, 25–30 kg/m2; obese, >30 kg/m2; <25 kg/m2 is used as reference