Objective: To identify distinct trajectories of antipsychotic use prior to and during pregnancy and describe the associated maternal and birth characteristics. Methods: We conducted a population-based cohort study of births (2005–2012) using linked administrative data in New South Wales, Australia. We used group-based trajectory modelling to classify trajectories of antipsychotic use in the 450 days prior to pregnancy and during pregnancy. We characterised women with different trajectories according to maternal sociodemographic characteristics, mental health diagnoses and hospitalisations, use of psychotropic medicines and birth outcomes. Results: Of 137,993 women who gave birth, 2741 (2.0%) were exposed to antipsychotics prior to or during pregnancy. We identified six trajectories of antipsychotic use: two involved short-term use of low daily doses prior to pregnancy (51.1%), while three involved long-term use of low (20.9%), moderate (11.0%) and high (2.0%) daily doses throughout pregnancy. One trajectory (15.0%) involved increasing use during pregnancy. Women with long-term use were more likely to have a schizophrenia or bipolar disorder diagnosis, to have used multiple psychotropics and to have a mental health hospitalisation during pregnancy. Overall, women using antipsychotics had elevated rates of adverse birth outcomes compared to unexposed women. Women with the greatest antipsychotic exposure had the highest rates of gestational diabetes and gestational hypertension. Conclusion: Women using antipsychotics around pregnancy are heterogeneous, with varying patterns of use and associated birth outcomes, reflecting underlying differences in the indications for treatment and/or severity of illness. This diversity should be considered when developing clinical guidelines and designing safety studies.