The research literature indicates that problematic substance use as a form of health behaviour is poorly understood, being sometimes viewed as deviance, at other times as a disease, and most often as a combination of these states. The use of substances by women who are pregnant or new parents is often conceptualised within an individualised framework. Yet drinking alcohol and using other drugs during pregnancy and early parenthood cuts across social divisions and is shaped by socio‐structural contexts including health care. There is a growing body of literature that critically examines public health interventions that are aimed at implementing harm reduction and health promotion techniques in service delivery to help pregnant and early parenting women who are identified as problem substance users. We examine qualitative data from representatives of a recent harm reduction intervention, focusing, in particular, on providers’ individual conceptualisations of the problematic behaviour. Our results show that most study participants regard any substance use during pregnancy, birth and the postpartum period as fundamentally unacceptable. This framing of problematic substance use is accomplished via gendered responsibilisation of women as foetal incubators and primary caregivers of infants. We discuss our results in light of the current literature and suggest policy implications.