Table 6.

Trimester-specific associations with the risk of preterm birth (categorical variable) (n = 11,123). Statistically significant variables (P < 0.05) emerging from the univariate analyses (see Table 4) were entered in the final model

	Effect size (ORa): unadjusted	Effect size (ORa): adjusted	95% CI	P value
1st trimester
Repetitive boring tasks	1.22	1.25	1.04, 1.50	0.016
3rd trimester
Bend and stoop	0.60	0.73	0.63, 0.84	<0.001
Night shifts	0.48	0.67	0.47, 0.95	0.025

^a OR odds ratio, CI 95% confidence interval