Design complexity (DC) is a decisive factor for a feasible and cost-effective product development. As DC increases, product development becomes more costly given the impact of complexity in the development time, manufacturing processes and development environment. Within the development environment, greater implications of DC are observed in the development of highly regulated products. This is the case of medical devices that are regulated by the Food and Drug Administration (FDA) in the Unites States. The FDA regulation requirements have a strong influence in the overall landscape of medical device development (MDD), with control over the development process, manufacturing and surveillance of medical devices in the market. This paper studies the relationship between medical device complexity and the regulations, where a combination of complexity metrics is used to explain FDA’s decision time. This relationship is evaluated for hip replacement devices that were approved by FDA in recent years and that have the same risk classification. Although complexity metrics have been developed for multiple applications, a quantification of complexity for medical devices was not found prior to this work. Product complexity metrics can aid MDD to increase an understanding about the design and its implications.