Overview of spontaneous preterm birth: a complex and multifactorial phenotype.

The phenotype of spontaneous preterm birth (SPTB) refers to the biochemical and physical characteristics present at the time of preterm delivery. These are the result of the processes that cause this complication. The lack of understanding about the etiologies and our inability to prevent SPTB are because of the complex nature and multiple processes responsible for maintenance of pregnancy and the transition to labor. Any of these processes, when activated prematurely, may lead to SPTB. This article provides an overview of the SPTB phenotype, which may assist with future attempts to reduce in the incidence of SPTB.