In the first article of this series, the potential benefits of a classification system for preterm birth were articulated and a brief history of attempts to classify preterm birth was presented. In this article, our goal is to raise many of the issues that need to be addressed and the decisions that need to be made to create a preterm birth classification system. As in the other articles in this series, the authors were brought together as a direct result of the Global Alliance to Prevent Prematurity and Stillbirth (GAPPS) meeting with instructions to determine the need for such a classification system, to define the issues related to creating a preterm birth classification system, and to present a prototype classification system for general consideration.

In addition to discussing the issues that need to be resolved before a classification system can be created, we also intend to cause readers to consider conceptual issues that may have hindered progress toward better understanding preterm birth. These include the assumption that the clinical presentation for delivery defines distinct causes and acceptance of the arbitrary gestational age boundaries that define prematurity. In writing this commentary, we began with many diverse opinions regarding the development of a classification system for preterm birth. We found that, by isolating each issue and posing a specific question regarding the issue, we could better understand the principles on which to base a classification system and, eventually, came to a consensus on each of the issues. We have tried to identify and emphasize clearly superior options among the possible choices, although noting other potential options and the rationale for our choices.