Severe mental illness tends to occur and recur among women in the reproductive period. Both the disorders and the treatments may have effects on the mother and the foetus. The clinician hence is often in a dilemma when treating pregnant women with severe mental illness and is challenged with ethical issues related to decision making in this regard. Both treatment and non treatment are not without risks and this is particularly challenging if the mother has active symptoms and cannot make decisions because of impaired capacity. This paper highlights some of these ethical and clinical dilemmas through case vignettes based on data from a specialised perinatal psychiatry service.