Contraception is often a taken-for-granted element of actively heterosexual women’s lives. Yet while modern contraceptives have technically enhanced women’s ability to control their fertility, the history of women’s struggles to achieve this control shows the importance of understanding the social context within which women’s contraceptive decisions are situated. Previous feminist studies of contraception in the UK have tended to concentrate either on aspects of medicine or on heterosexuality. Whilst both areas have highlighted the need to understand how power relationships structure women’s contraceptive experiences, these two aspects have not been integrated adequately. There has also been a tendency to focus research on younger women, and mature women’s ongoing use of contraception has generally been overlooked. This thesis is based on qualitative interviews with twenty-two mid-life British women aged between 30 and 40, as well as observations at a family planning clinic. It demonstrates that only by giving full consideration to the extent and complexity of the power relationships surrounding contraception can an understanding of women’s decisions and everyday practices be achieved. The concept of ‘subjective power’ is developed to explore how these women make strategic and creative use of circulating discourses, interact with disciplinary regimes, and situate themselves within multi-faceted webs of power relationships, such as in relation to the institutions of medicine, the media, and heterosexuality. The embodied nature of both the risk of pregnancy and the use of contraceptive technologies is argued to lead the women to assert a right of bodily autonomy. Yet this assertion conflicts with their expectation of equitable coupledom within heterosexuality and their routine consideration of men’s preferences. In addition, this thesis will show that taking ‘proper’ responsibility for preventing pregnancy constructs women as respectable, yet may increase their risk of contracting sexually transmitted infections.