RESEARCH ARTICLE Timing of Histologic Progression from Chorio- Deciduitis to Chorio-Deciduo-Amnionitis in the Setting of Preterm Labor and Preterm Premature Rupture of Membranes with Sterile Amniotic Fluid

Background Histologic chorio-deciduitis and chorio-deciduo-amnionitis (amnionitis) in extra-placental membranes are known to represent the early and advanced stages of ascending intra-uterine infection. However, there are no data in humans about the time required for chorio-deciduitis to develop and for chorio-deciduitis without amnionitis to progress to chorio-deciduitis with amnionitis, and the effect of prolongation of pregnancy on the devel-opment of chorio-deciduitis and amnionitis in patients with preterm labor and intact mem-branes (PTL) and preterm premature rupture of membranes (preterm-PROM). We examined these issues in this study. Methods The study population consisted of 289 women who delivered preterm (133 cases with PTL, and 156 cases with preterm-PROM) and who had sterile amniotic fluid (AF) defined as a negative AF culture and the absence of inflammation as evidenced by a matrix metallopro-teinase-8 (MMP-8) level <23 ng/ml. We examined the association between amniocentesis