Fig. 1: Illustration of cohort inclusion and pregnancy periods.

^aThe earliest date of mothers’ health data in each data source. ^bBaseline conditions included: demographics, maternal conditions and medication use. For HK analysis, maternal age at delivery and birth year were assessed at the date of delivery, body mass index (BMI) was assessed from LMP − 365 days to LMP − 1 day and all other covariates were assessed before LMP; for analysis in Nordic countries and New Zealand, medication use was assessed from LMP − 365 days to LMP − 1 day, and diagnoses were assessed from LMP − 365 days to delivery date; for Taiwan analysis, all covariates were assessed within 2 years before the date of delivery. ^cExposure window: (1) Period before pregnancy, (2) first trimester: LMP to LMP + 90 days, (3) second trimester: LMP + 91 days to LMP + 180 days, and (4) third trimester: LMP + 181 days to delivery date. ^dEarliest of: date of ADHD diagnosis, date of first ADHD medication prescription, date of death, end of database catchment period.