The role of inflammation and infection in preterm birth

Abstract

Inflammation has been implicated in the mechanisms responsible for preterm and term parturition, as well as fetal injury. Out of all of the suspected causes of preterm labor and delivery, infection and/or inflammation is the only pathological process for which both a firm causal link with preterm birth has been established and a molecular pathophysiology defined. Inflammation has also been implicated in the mechanism of spontaneous parturition at term. Most cases of histopathological inflammation and histological chorioamnionitis, both in preterm and term labor, are sub-clinical in nature. The isolation of bacteria in the amniotic fluid, known as microbial invasion of the amniotic cavity, is a pathological finding; the frequency of which is dependent upon the clinical presentation and gestational age. This article reviews the role of inflammation in preterm and term parturition.

Figure 1.

The most common pathway of intrauterine infection is the ascending route. (Reproduced, with permission, from Romero R, Mazor M. Infection and preterm labor. Clin Obstet Gynaecol 1982; 9:593–607).

Figure 2.

Fetal target organs during the fetal inflammatory response syndrome. CSFs, colony-stimulating factors; MMPs, matrix metalloproteinases.

Figure 3.

Classification and procedure-to-delivery intervals of patients according to amniotic fluid and fetal plasma interleukin-6 (IL-6) concentrations. A white color in the fetal or amniotic fluid (AF) compartment represents a low fetal plasma (FP) or amniotic fluid IL-6 concentration, respectively. Black in the fetal or amniotic fluid compartment denotes elevated fetal plasma or amniotic fluid IL-6 concentration.