Exposures under investigation and exposure comparison groups
Exposure in first trimester of pregnancy to any macrolide (ATC code
J01FA), and five specific macrolide subclass erythromycin (ATC code
J01FA01), spiramycin (ATC code J01FA02), clarithromycin (ATC code
J01FA09), azithromycin (ATC code J01FA10) and clindamycin (ATC code
J01FF01)). Two types of exposure comparison groups were used: no
antibiotic exposure during pregnancy (primary comparison) and exposure
to drugs other than antibiotics, excluding vitamins and minerals
(secondary comparison).
Macrolides are used as an alternative for pregnant women who are
allergic to penicillins which is considered relatively safer compared to
other types of antibiotics.13 Hence we performed
sensitivity analyses for selected significant results using penicillins
as the exposure comparison in order to account for any residual
confounding due to infection. This approach has also been used in other
studies.13,19,25