Figure 2.

A schematic representation of proposed model for labor at term. Amniotic expression of PTGS2 is minimal before term in the absence of clinical and histological chorioamnionitis (PTL), whereas there is a robust increase in the placental amnion at term before the onset of labor (TNL). Labor at term is largely associated with increased PTGS2 expression in the reflected amnion (TIL). Arrows indicate PGE₂ expression in the placental amnion and release into the amniotic fluid (TNL), which induces PTGS2 expression in the reflected amnion by a positive feedback mechanism (TIL). PTL, Preterm labor without clinical and histological chorioamnionitis.