BACKGROUND: The perceived risk/benefit balance of prescribed and over-the-counter (OTC) medicine, as well as complementary therapies, will significantly impact on an individual's decision-making to use medicine. For women who are pregnant or breastfeeding, this weighing of risks and benefits becomes immensely more complex because they are considering the effect on two bodies rather than one. Indeed the balance may lie in opposite directions for the mother and baby/fetus. The aim of this paper is to generate a discussion that focuses on the complexity around risk, responsibility and decision-making of medicine use by pregnant and breastfeeding women. We will also consider the competing discourses that pregnant and breastfeeding women encounter when making decisions about medicine. DISCUSSION: Women rely not only on biomedical information and the expert knowledge of their health care professionals but on their own experiences and cultural understandings as well. When making decisions about medicines, pregnant and breastfeeding women are influenced by their families, partners and their cultural societal norms and expectations. Pregnant and breastfeeding women are influenced by a number of competing discourses. "Good" mothers should manage and avoid any risks, thereby protecting their babies from harm and put their children's needs before their own - they should not allow toxins to enter the body. On the other hand, "responsible" women take and act on medical advice - they should take the medicine as directed by their health professional. This is the inherent conflict in medicine use for maternal bodies. SUMMARY: The increased complexity involved when one body's actions impact the body of another - as in the pregnant and lactating body - has received little acknowledgment. We consider possibilities for future research and methodologies. We argue that considering the complexity of issues for maternal bodies can improve our understanding of risk and public health education.