Spontaneous preterm birth (SPTB) is a well-known cause of maternal and neonatal morbidity. The search for the underlying pathways, documentation of the genetic causes, and identification of markers of spontaneous PTB have been marginally successful due to the fact that it is highly complex, with numerous processes that lead to a final common pathway. There is a great need for a comprehensive, consistent, and uniform classification system, which will be useful in identifying mechanisms, assigning prognosis, aiding in clinical management, and can identify areas of interest for intervention and future study. Effective classification systems must overcome obstacles including the lack of widely accepted definitions and uncertainty about inclusion of classifying features (e.g., presentation at delivery and multiple gestations) and levels of detail of these features. The optimal classification system should be based on the clinical phenotype, including characteristics of the mother, fetus, placenta, and the presentation for delivery. We present a proposed phenotyping system for spontaneous PTB. Future classification systems must establish a universally accepted set of definitions and a standardized clinical workup for all PTBs including the minimum clinical data to be collected and the laboratory and pathologic evaluation that should be completed.
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