Table 3.

Association between antibiotic exposure per gestational trimester and preterm birth (exclusive use in each trimester), using all non-users as reference and expressed as ORs and 95% CIs

	In mothers without selected chronic comorbidities	In mothers with selected chronic comorbidities
Three months pre-pregnancy	1.01 (0.95–1.07)	1.02 (0.81–1.27)
First trimester	1.08 (1.02–1.14)	1.43 (1.16–1.75)
Second trimester	1.33 (1.26–1.40)	1.53 (1.26–1.85)
Third trimester	0.82 (0.77–0.88)	0.80 (0.63–1.03)

All analyses are adjusted for chronic comorbidities, maternal age, BMI, tobacco consumption, exposure to other drugs, mother’s country of birth, history of stillbirth and history of miscarriages.