Considerable evidence suggests that modifiable risk factors for adverse pregnancy outcomes such as preterm birth and low birthweight include obesity, sedentary behavior, and infections. There is a growing consensus that the preconceptional and interconceptional periods may be an ideal time for preventive intervention targeting these risk factors; enhancing health before pregnancy would subsequently reduce the risk for poor pregnancy outcomes. This paper provides an overview of the development of a health behavior intervention, Strong Healthy Women, that aims to improve women's preconceptional and interconceptional health. We describe the rationale, delivery, and targeted outcomes of the program, as well as the design of an ongoing trial currently testing program efficacy. The content areas are also discussed and include pregnancy-conception, stress, physical activity, nutrition, infection, sources of smoke in the home, and substance use. This intervention protocol may offer researchers and healthcare professionals a framework for designing other programs aiming to improve women's preconceptional health.