Dataset exclusions
We applied the following exclusions to our original dataset:
1) the South East (SE) Ireland registry was excluded from the dataset because there were no registrations with a first trimester antibiotic exposure; Reunion-France and Ukraine registries were excluded because they recorded no macrolide exposure;
2) TOPFAs were excluded from the Emilia Romagna registry as information on medications is only available for LB and stillbirths;
3) registrations with isolated hip dislocation/dysplasia were excluded based on the known association with birthweight and potential for confounding;
4) registrations with mothers with epilepsy or pregestational diabetes, or mothers who took anti-epileptics or hypoglycaemic agents were excluded due to the known association with CA;
5) registrations which had antibiotic exposures of unknown timing or missing description were excluded (90% of these were from three registries: Saxony-Anhalt-Germany, Wielkopolska-Poland and Poland excluding Wielkopolska). These exclusions reduced the dataset from 170,062 to 145,936 registrations as shown in Figure 1.