In recent decades overnutrition and obesity have been presented as a looming threat to the health and wellbeing of children and infants, most notably in western industrialised societies. However, this threat is not simply limited to 'children' who are 'over fed' by their 'parents'. Increasingly, maternal overweight and obesity are said to inhibit conception, cause recurrent miscarriage, pose a serious threat to the development and health of the foetus and have long-term implications for the future wellbeing of the child. Parental responsibility looms large in these discourses, in which women in particular are held responsible for the future (fat free) health of their offspring from the womb to the tomb. In this article, it is argued that core assumptions at the heart of obesity science have been taken up uncritically in medical arenas focused on conception, pregnancy and reproduction and that this is providing new opportunities for the surveillance, regulation and disciplining of 'threatening' (fat) female bodies. It is shown that although all women of a reproductive age are being brought under the gaze of this deeply punitive medico-moral discourse, it is the bodies, lives and bedrooms of marginalised women that are singled out as posing the greatest 'risk' to their offspring and then targeted for even greater degrees of health/State intervention and surveillance.