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Introduction Recent evidence from the USA and Nordic countries suggests a possible association between psychostimulant use during gestation and adverse pregnancy and birth outcomes. Objectives and Approach We employed a distributed cohort analysis using linked administrative data for women who gave birth in New South Wales (NSW; Australia) and Ontario (Canada), whereby a common protocol was implemented separately in each jurisdiction. The study population comprised women who were hospitalized for a singleton delivery over an 8 (NSW) and 4 (Ontario) year period, respectively, with the NSW cohort restricted to social security beneficiaries. Psychostimulant exposure was defined as at least one dispensing of methylphenidate, amphetamine, dextroamphetamine or lisdexamfetamine during pregnancy. We examined the risk of maternal and neonatal outcomes among psychostimulant exposed mothers compared with unexposed mothers. Results There were 140,356 eligible deliveries in NSW and 449,499 in Ontario during the respective study periods. Fewer than 1% of these pregnancies were exposed to psychostimulants during gestation, although use was higher in Ontario (0.30% vs 0.11% in NSW). Preliminary unadjusted analyses indicated possible associations between psychostimulant use in pregnancy and higher risks of pre-term birth (relative risk [RR] 1.7, 95% confidence interval [CI] 1.4-2.0 (Ontario); RR 1.8, 95% CI 1.2-2.6 (NSW)) and pre-eclampsia (RR 2.0, 95% CI 1.5-2.6 (Ontario); RR 2.0, 95% CI 1.2-3.5 (NSW)). Similarly, psychostimulant use was associated with higher risks of low birthweight (RR 1.6, 95% CI 1.3-1.9 (Ontario); RR 2.0, 95% CI 1.3-3.0 (NSW)) and admission to neonatal intensive care (RR 2.1, 95% CI 1.9-2.3 (Ontario); RR 1.5, 95% CI 1.1-1.9 (NSW)). Conclusion / Implications Unadjusted analyses indicate an increased risk of adverse maternal and birth outcomes associated with psychostimulant exposure during pregnancy, potentially representing a placental effect. We are currently refining the analyses, employing propensity score methods to adjust for confounding.