The etiology of preterm birth is difficult to classify. It is usually divided into three clinical types according to its clinical presentation: medically indicated; caused by ruptured membranes; and spontaneous or idiopathic. However, this classification is controversial, imprecise and can result in multiple interpretations when applied.
Objective: To design an etiologically based classification of preterm birth, and to design a system to easily assign each case during the perinatal period.
Methods: Review of literature, qualitative analysis using consensus methods through nominal group technique, and quantitative analysis of a pilot study using a first version of the algorithm.
Results: A classification is made to establish a general division between the "primary cause" and "associated causes" of preterm birth, that allows remote causes or risk factors to be included. The primary cause includes seven categories: inflammatory (ruptured membranes and related); vascular (intrauterine growth restriction and related); maternal-local; maternal-systemic; fetal pathology; fetal distress; idiopathic. The medically indicated preterm birth is defined as a previous or independent category and so is compatible with the other, previously mentioned causes . An algorithm was designed to make it easier to classify the primary cause of preterm birth using a flowchart.
Conclusions: A pragmatic classification of preterm birth is proposed that may help to achieve better precision and agreement between clinicians.