ObjectivesTo investigate the perceived risk of psychotropic and mental illness exposures (1) during pregnancy or (2) while breastfeeding on offspring neurodevelopment, and factors associated with this perception in women with past/current mental illness.DesignCross-sectional, web-based study.SettingNationwide in Norway, June 2020–June 2021.ParticipantsWomen aged 18–55 years who were pregnant, recent mothers or planning a pregnancy, and had been offered antidepressants in the last 5 years.Primary and secondary outcome measuresPerceived risk of prenatal and breastmilk exposure to psychotropic medications and maternal mental illness on offspring neurodevelopmental outcomes.ResultsWe included 448 women: 234 pregnant, 146 mothers and 68 planning a pregnancy. On a 0–10 scale, women perceived antidepressants as least harmful both (1) in pregnancy (mean score 4.2, 95% CI 3.6 to 4.8) and (2) while breastfeeding (mean score 3.8, 95% CI 3.3 to 4.4), relative to antipsychotics, anxiety/sleeping medication or antiepileptics (mean score range: 6.3–6.5 during pregnancy, 5.5–6.2 while breastfeeding). Many participants were unfamiliar with psychotropics other than antidepressants. The perceived risk of mental illness exposure exceeded that of antidepressants (mean score range 5.6–5.9) in both exposure periods. Using general linear models, factors associated with greater antidepressant risk perception in both exposure periods included having lower education, non-Norwegian native language, and employment status (range mean score difference (β): 2.07–6.07). For pregnant women and mothers, there was an inverse association between perceived risk and the perceived antidepressant effectiveness in both exposure periods (range of β: −0.18 to –0.25).ConclusionsIn women with past/current mental illness, the perceived risk of antidepressant exposure on child neurodevelopment was lower than that for maternal mental illness. Other psychotropic medications were perceived as more harmful. As medication risk perception influences the decision-making regarding treatment of mental illness, pre- and pregnancy counselling should target women with characteristics associated with higher perceived risk.