Preterm labor is defined as labor that begins before 37 completed weeks of pregnancy. More than 12% of infants born in the USA are preterm. At least 40% of preterm births are associated with intrauterine infection. Toll-like receptors (TLRs) are members of a family of cell-surface proteins responsible for recognition of a diverse spectrum of bacterial, viral and fungal pathogens. TLRs initiate the host innate (i.e. non-adaptive) immune response, inducing a proinflammatory cascade involving cytokines, chemokines, prostaglandins, and other effector molecules that result in the characteristic phenomena of labor, such as uterine contractions and rupture of fetal membranes. These cascades may also be activated by mechanisms that are not primarily infectious but are accompanied by inflammatory responses. Now that the molecular mechanisms linking infection and labor have been, to a large extent, elucidated, the challenge is to identify points of overlap with non-infectious causes of labor and to find intervention strategies that can minimize the negative impact of preterm delivery.
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