The association between psychostimulant use in pregnancy and adverse maternal and neonatal outcomes: results from a distributed analysis in two similar jurisdictions

Background Conflicting evidence suggests a possible association between use of prescribed psychostimulants during pregnancy and adverse perinatal outcomes. Methods We conducted population-based cohort studies including pregnancies conceived between April 2002 and March 2017 (Ontario, Canada; N = 554 272) and January 2003 to April 2011 [New South Wales (NSW), Australia; N = 139 229]. We evaluated the association between exposure to prescription amphetamine, methylphenidate, dextroamphetamine or lisdexamfetamine during pregnancy and pre-eclampsia, placental abruption, preterm birth, low birthweight, small for gestational age and neonatal intensive care unit admission. We used inverse probability of treatment weighting based on propensity scores to balance measured confounders between exposed and unexposed pregnancies. Additionally, we restricted the Ontario cohort to social security beneficiaries where supplementary confounder information was available. Results In Ontario and NSW respectively, 1360 (0.25%) and 146 (0.10%) pregnancies were exposed to psychostimulants. Crude analyses indicated associations between exposure and nearly all outcomes [OR range 1.15–2.16 (Ontario); 0.97–2.20 (NSW)]. Nearly all associations were attenuated after weighting. Pre-eclampsia was the exception: odds remained elevated in the weighted analysis of the Ontario cohort (OR 2.02, 95% CI 1.42–2.88), although some attenuation occurred in NSW (weighted OR 1.50, 95% CI 0.77–2.94) and upon restriction to social security beneficiaries (weighted OR 1.24, 95% CI 0.64–2.40), and confidence intervals were wide. Conclusions We observed higher rates of outcomes among exposed pregnancies, but the attenuation of associations after adjustment and likelihood of residual confounding suggests psychostimulant exposure is not a major causal factor for most measured outcomes. Our findings for pre-eclampsia were inconclusive; exposed pregnancies may benefit from closer monitoring.